Chromium 前端form表单提交过程分析c++

一、本文以一个简单的 HTML 表单，包罗两个文本输入框和一个提交按钮：

1. <form action="demo_form.php">
2.   First name: <input type="text" name="fname"><br>
3.   Last name: <input type="text" name="lname"><br>
4.   <input type="submit" value="提交">
5. </form>

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测试时候可以打开菜鸟教程在线编辑器 (runoob.com)运行以上代码
二、看下c++form表单接口定义：

2.1)、form接口定义文件：

third_party\blink\renderer\core\html\forms\html_form_element.idl
method="get|post|dialog"

2. // https://html.spec.whatwg.org/C/#the-form-element
4. [
5.     Exposed=Window,
6.     HTMLConstructor,
7.     LegacyOverrideBuiltIns
8. ] interface HTMLFormElement : HTMLElement {
9.     [CEReactions, Reflect=accept_charset] attribute DOMString acceptCharset;
10.     [CEReactions, URL] attribute USVString action;
11.     [CEReactions, Reflect, ReflectOnly=("on","off"), ReflectMissing="on", ReflectInvalid="on"] attribute DOMString autocomplete;
12.     [CEReactions] attribute DOMString enctype;
13.     [CEReactions] attribute DOMString encoding;
14.     [CEReactions] attribute DOMString method;
15.     [CEReactions, Reflect] attribute DOMString name;
16.     [CEReactions, Reflect] attribute boolean noValidate;
17.     [CEReactions, Reflect] attribute DOMString target;
18.     [CEReactions, Reflect] attribute DOMString rel;
19.     [SameObject, PutForwards=value] readonly attribute DOMTokenList relList;
21.     readonly attribute HTMLFormControlsCollection elements;
22.     readonly attribute long length;
23.     [ImplementedAs=item] getter Element (unsigned long index);
24.     // FIXME: This getter should not have [NotEnumerable].
25.     [NotEnumerable] getter (RadioNodeList or Element) (DOMString name);
27.     [ImplementedAs=submitFromJavaScript] void submit();
28.     [RaisesException] void requestSubmit(optional HTMLElement? submitter = null);
29.     [CEReactions] void reset();
30.     boolean checkValidity();
31.     boolean reportValidity();
32. };

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2.2）、blink下form接口实现：

third_party\blink\renderer\core\html\forms\html_form_element.h
third_party\blink\renderer\core\html\forms\html_form_element.cc
用于查找和遍历form元素

2. #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_HTML_FORM_ELEMENT_H_
3. #define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_HTML_FORM_ELEMENT_H_
5. #include "third_party/blink/renderer/core/core_export.h"
6. #include "third_party/blink/renderer/core/html/forms/html_form_control_element.h"
7. #include "third_party/blink/renderer/core/html/forms/radio_button_group_scope.h"
8. #include "third_party/blink/renderer/core/html/html_element.h"
9. #include "third_party/blink/renderer/core/loader/form_submission.h"
10. #include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_map.h"
12. namespace blink {
14. class DOMTokenList;
15. class Event;
16. class HTMLFormControlElement;
17. class HTMLFormControlsCollection;
18. class HTMLImageElement;
19. class ListedElement;
20. class RelList;
21. class V8UnionElementOrRadioNodeList;
23. class CORE_EXPORT HTMLFormElement final : public HTMLElement {
24.   DEFINE_WRAPPERTYPEINFO();
26. public:
27.   enum RelAttribute {
28.     kNone = 0,
29.     kNoReferrer = 1 << 0,
30.     kNoOpener = 1 << 1,
31.     kOpener = 1 << 2,
32.   };
34.   explicit HTMLFormElement(Document&);
35.   ~HTMLFormElement() override;
36.   void Trace(Visitor*) const override;
38.   HTMLFormControlsCollection* elements();
39.   void GetNamedElements(const AtomicString&, HeapVector<Member<Element>>&);
41.   unsigned length() const;
42.   HTMLElement* item(unsigned index);
44.   String action() const;
45.   void setAction(const AtomicString&);
47.   String enctype() const { return attributes_.EncodingType(); }
48.   void setEnctype(const AtomicString&);
50.   String encoding() const { return attributes_.EncodingType(); }
51.   void setEncoding(const AtomicString& value) { setEnctype(value); }
53.   DOMTokenList& relList() const;
55.   bool HasRel(RelAttribute relation) const;
57.   bool ShouldAutocomplete() const;
59.   void Associate(ListedElement&);
60.   void Disassociate(ListedElement&);
61.   void Associate(HTMLImageElement&);
62.   void Disassociate(HTMLImageElement&);
63.   void DidAssociateByParser();
65.   void PrepareForSubmission(const Event*,
66.                             HTMLFormControlElement* submit_button);
67.   void submitFromJavaScript();
68.   void requestSubmit(ExceptionState& exception_state);
69.   void requestSubmit(HTMLElement* submitter, ExceptionState& exception_state);
70.   void reset();
72.   void AttachLayoutTree(AttachContext& context) override;
73.   void DetachLayoutTree(bool performing_reattach) override;
75.   void SubmitImplicitly(const Event&, bool from_implicit_submission_trigger);
77.   String GetName() const;
79.   bool NoValidate() const;
81.   const AtomicString& Action() const;
83.   String method() const;
84.   void setMethod(const AtomicString&);
85.   FormSubmission::SubmitMethod Method() const { return attributes_.Method(); }
87.   // Find the 'default button.'
88.   // https://html.spec.whatwg.org/C/#default-button
89.   HTMLFormControlElement* FindDefaultButton() const;
91.   bool checkValidity();
92.   bool reportValidity();
93.   bool MatchesValidityPseudoClasses() const final;
94.   bool IsValidElement() final;
96.   RadioButtonGroupScope& GetRadioButtonGroupScope() {
97.     return radio_button_group_scope_;
98.   }
100.   const ListedElement::List& ListedElements(
101.       bool include_shadow_trees = false) const;
102.   const HeapVector<Member<HTMLImageElement>>& ImageElements();
104.   V8UnionElementOrRadioNodeList* AnonymousNamedGetter(const AtomicString& name);
105.   void InvalidateDefaultButtonStyle() const;
107.   // 'construct the entry list'
108.   // https://html.spec.whatwg.org/C/#constructing-the-form-data-set
109.   // Returns nullptr if this form is already running this function.
110.   FormData* ConstructEntryList(HTMLFormControlElement* submit_button,
111.                                const WTF::TextEncoding& encoding);
113.   uint64_t UniqueRendererFormId() const { return unique_renderer_form_id_; }
115.   void InvalidateListedElementsIncludingShadowTrees();
117. private:
118.   InsertionNotificationRequest InsertedInto(ContainerNode&) override;
119.   void RemovedFrom(ContainerNode&) override;
120.   void FinishParsingChildren() override;
122.   void HandleLocalEvents(Event&) override;
124.   void ParseAttribute(const AttributeModificationParams&) override;
125.   bool IsURLAttribute(const Attribute&) const override;
126.   bool HasLegalLinkAttribute(const QualifiedName&) const override;
128.   NamedItemType GetNamedItemType() const override {
129.     return NamedItemType::kName;
130.   }
132.   void SubmitDialog(FormSubmission*);
133.   void ScheduleFormSubmission(const Event*,
134.                               HTMLFormControlElement* submit_button);
136.   void CollectListedElements(
137.       const Node& root,
138.       ListedElement::List& elements,
139.       ListedElement::List* elements_including_shadow_trees = nullptr,
140.       bool in_shadow_tree = false) const;
141.   void CollectImageElements(Node& root, HeapVector<Member<HTMLImageElement>>&);
143.   // Returns true if the submission should proceed.
144.   bool ValidateInteractively();
146.   // Validates each of the controls, and stores controls of which 'invalid'
147.   // event was not canceled to the specified vector. Returns true if there
148.   // are any invalid controls in this form.
149.   bool CheckInvalidControlsAndCollectUnhandled(ListedElement::List*);
151.   Element* ElementFromPastNamesMap(const AtomicString&);
152.   void AddToPastNamesMap(Element*, const AtomicString& past_name);
153.   void RemoveFromPastNamesMap(HTMLElement&);
155.   typedef HeapHashMap<AtomicString, Member<Element>> PastNamesMap;
157.   FormSubmission::Attributes attributes_;
158.   Member<PastNamesMap> past_names_map_;
160.   RadioButtonGroupScope radio_button_group_scope_;
162.   // Do not access listed_elements_ directly. Use ListedElements() instead.
163.   ListedElement::List listed_elements_;
164.   // Do not access listed_elements_including_shadow_trees_ directly. Use
165.   // ListedElements(true) instead.
166.   ListedElement::List listed_elements_including_shadow_trees_;
167.   // Do not access image_elements_ directly. Use ImageElements() instead.
168.   HeapVector<Member<HTMLImageElement>> image_elements_;
170.   uint64_t unique_renderer_form_id_;
172.   base::OnceClosure cancel_last_submission_;
174.   bool is_submitting_ = false;
175.   bool in_user_js_submit_event_ = false;
176.   bool is_constructing_entry_list_ = false;
178.   bool listed_elements_are_dirty_ : 1;
179.   bool listed_elements_including_shadow_trees_are_dirty_ : 1;
180.   bool image_elements_are_dirty_ : 1;
181.   bool has_elements_associated_by_parser_ : 1;
182.   bool has_elements_associated_by_form_attribute_ : 1;
183.   bool did_finish_parsing_children_ : 1;
184.   bool is_in_reset_function_ : 1;
186.   Member<RelList> rel_list_;
187.   unsigned rel_attribute_ = 0;
188. };
190. }  // namespace blink
192. #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_HTML_FORM_ELEMENT_H_

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2.3）、v8下form接口实现：

        out\Debug\gen\third_party\blink\renderer\bindings\core\v8\v8_html_form_element.h
       out\Debug\gen\third_party\blink\renderer\bindings\core\v8\v8_html_form_element.cc
截取部分定义:

1. void MethodAttributeGetCallback(const v8::FunctionCallbackInfo<v8::Value>& info) {
2.   
3. RUNTIME_CALL_TIMER_SCOPE_DISABLED_BY_DEFAULT(info.GetIsolate(), "Blink_HTMLFormElement_method_Getter");
4. BLINK_BINDINGS_TRACE_EVENT("HTMLFormElement.method.get");
8. v8::Isolate* isolate = info.GetIsolate();
9. v8::Local<v8::Object> v8_receiver = info.This();
10. HTMLFormElement* blink_receiver = V8HTMLFormElement::ToWrappableUnsafe(isolate, v8_receiver);
11. auto&& return_value = blink_receiver->method();
12. bindings::V8SetReturnValue(info, return_value, isolate, bindings::V8ReturnValue::kNonNullable);
13. }
15. void MethodAttributeSetCallback(const v8::FunctionCallbackInfo<v8::Value>& info) {
16.   
17. RUNTIME_CALL_TIMER_SCOPE_DISABLED_BY_DEFAULT(info.GetIsolate(), "Blink_HTMLFormElement_method_Setter");
18. BLINK_BINDINGS_TRACE_EVENT("HTMLFormElement.method.set");
21. v8::Isolate* isolate = info.GetIsolate();
22. const ExceptionContextType exception_context_type = ExceptionContextType::kAttributeSet;
23. const char* const class_like_name = "HTMLFormElement";
24. const char* const property_name = "method";
25. ExceptionState exception_state(isolate, exception_context_type, class_like_name, property_name);
27. // [CEReactions]
28. CEReactionsScope ce_reactions_scope;
30. v8::Local<v8::Object> v8_receiver = info.This();
31. HTMLFormElement* blink_receiver = V8HTMLFormElement::ToWrappableUnsafe(isolate, v8_receiver);
32. v8::Local<v8::Value> v8_property_value = info[0];
33. auto&& arg1_value = NativeValueTraits<IDLString>::NativeValue(isolate, v8_property_value, exception_state);
34. if (UNLIKELY(exception_state.HadException())) {
35.   return;
36. }
37. blink_receiver->setMethod(arg1_value);
39. }

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2.4)、form_datat数据填充接口：

     FormData用来构建FormSubmission对象重要存储form表单内的元素参数：
      比方： 
 First name: <input type="text" name="fname"><br>
 Last name: <input type="text" name="lname"><br> 
会转换成FirstName=Mickey&LastName=Mouse，末了放到url请求参数内里。
结果：
https://www.runoob.com/try/demo_source/demo-form.php?FirstName=Mickey&LastName=Mouse
hird_party\blink\renderer\core\html\forms\form_data.idl

1. // https://xhr.spec.whatwg.org/#interface-formdata
3. typedef (File or USVString) FormDataEntryValue;
5. [
6.     Exposed=(Window,Worker)
7. ] interface FormData {
8.     [RaisesException] constructor(optional HTMLFormElement form, optional HTMLElement? submitter = null);
9.     void append(USVString name, USVString value);
10.     [CallWith=ScriptState] void append(USVString name, Blob value, optional USVString filename);
11.     [ImplementedAs=deleteEntry] void delete(USVString name);
12.     FormDataEntryValue? get(USVString name);
13.     sequence<FormDataEntryValue> getAll(USVString name);
14.     boolean has(USVString name);
15.     void set(USVString name, USVString value);
16.     void set(USVString name, Blob value, optional USVString filename);
17.     iterable<USVString, FormDataEntryValue>;
18. };

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blink和v8定义：
third_party\blink\renderer\core\html\forms\form_data.h
third_party\blink\renderer\core\html\forms\form_data.cc

1. #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_FORM_DATA_H_
2. #define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_FORM_DATA_H_
4. #include "third_party/blink/renderer/bindings/core/v8/iterable.h"
5. #include "third_party/blink/renderer/bindings/core/v8/v8_sync_iterator_form_data.h"
6. #include "third_party/blink/renderer/bindings/core/v8/v8_typedefs.h"
7. #include "third_party/blink/renderer/core/core_export.h"
8. #include "third_party/blink/renderer/core/html/html_element.h"
9. #include "third_party/blink/renderer/platform/heap/garbage_collected.h"
10. #include "third_party/blink/renderer/platform/network/encoded_form_data.h"
11. #include "third_party/blink/renderer/platform/wtf/forward.h"
12. #include "third_party/blink/renderer/platform/wtf/text/text_encoding.h"
14. namespace blink {
16. class Blob;
17. class File;
18. class FormControlState;
19. class HTMLFormElement;
20. class ScriptState;
21. class ExecutionContext;
23. class CORE_EXPORT FormData final : public ScriptWrappable,
24.                                    public PairSyncIterable<FormData> {
25.   DEFINE_WRAPPERTYPEINFO();
27. public:
28.   static FormData* Create(ExceptionState& exception_state) {
29.     return MakeGarbageCollected<FormData>();
30.   }
31.   static FormData* Create(HTMLFormElement* form,
32.                           ExceptionState& exception_state);
33.   static FormData* Create(HTMLFormElement* form,
34.                           HTMLElement* submitter,
35.                           ExceptionState& exception_state);
37.   explicit FormData(const WTF::TextEncoding&);
38.   // Clones form_data.  This clones |form_data.entries_| Vector, but
39.   // doesn't clone entries in it because they are immutable.
40.   FormData(const FormData& form_data);
41.   FormData();
42.   void Trace(Visitor*) const override;
44.   // FormData IDL interface.
45.   void append(const String& name, const String& value);
46.   void append(ScriptState*,
47.               const String& name,
48.               Blob*,
49.               const String& filename = String());
50.   void deleteEntry(const String& name);
51.   V8FormDataEntryValue* get(const String& name);
52.   HeapVector<Member<V8FormDataEntryValue>> getAll(const String& name);
53.   bool has(const String& name);
54.   void set(const String& name, const String& value);
55.   void set(const String& name, Blob*, const String& filename = String());
57.   // Internal functions.
59.   const WTF::TextEncoding& Encoding() const { return encoding_; }
60.   std::string Encode(const String& key) const;
61.   class Entry;
62.   const HeapVector<Member<const Entry>>& Entries() const { return entries_; }
63.   size_t size() const { return entries_.size(); }
64.   void append(const String& name, Blob*, const String& filename = String());
65.   void AppendFromElement(const String& name, int value);
66.   void AppendFromElement(const String& name, File* file);
67.   void AppendFromElement(const String& name, const String& value);
69.   // This flag is true if this FormData is created with a <form>, and its
70.   // associated elements contain a non-empty password field.
71.   bool ContainsPasswordData() const { return contains_password_data_; }
72.   void SetContainsPasswordData(bool flag) { contains_password_data_ = flag; }
74.   scoped_refptr<EncodedFormData> EncodeFormData(
75.       EncodedFormData::EncodingType = EncodedFormData::kFormURLEncoded);
76.   scoped_refptr<EncodedFormData> EncodeMultiPartFormData();
78.   void AppendToControlState(FormControlState& state) const;
79.   static FormData* CreateFromControlState(ExecutionContext& execution_context,
80.                                           const FormControlState& state,
81.                                           wtf_size_t& index);
83. private:
84.   void SetEntry(const Entry*);
85.   IterationSource* CreateIterationSource(ScriptState*,
86.                                          ExceptionState&) override;
88.   WTF::TextEncoding encoding_;
89.   // Entry pointers in entries_ never be nullptr.
90.   HeapVector<Member<const Entry>> entries_;
91.   bool contains_password_data_ = false;
92. };
94. // Represents entry, which is a pair of a name and a value.
95. // https://xhr.spec.whatwg.org/#concept-formdata-entry
96. // Entry objects are immutable.
97. class FormData::Entry final : public GarbageCollected<FormData::Entry> {
98. public:
99.   Entry(const String& name, const String& value);
100.   Entry(const String& name, Blob* blob, const String& filename);
101.   void Trace(Visitor*) const;
103.   bool IsString() const { return !blob_; }
104.   bool isFile() const { return blob_ != nullptr; }
105.   const String& name() const { return name_; }
106.   const String& Value() const { return value_; }
107.   Blob* GetBlob() const { return blob_.Get(); }
108.   CORE_EXPORT File* GetFile() const;
109.   const String& Filename() const { return filename_; }
111. private:
112.   const String name_;
113.   const String value_;
114.   const Member<Blob> blob_;
115.   const String filename_;
116. };
118. }  // namespace blink
120. #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_FORM_DATA_H_

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out\Debug\gen\third_party\blink\renderer\bindings\core\v8\v8_form_data.h
out\Debug\gen\third_party\blink\renderer\bindings\core\v8\v8_form_data.cc
截图部分实现：

1. void KeysOperationCallback(const v8::FunctionCallbackInfo<v8::Value>& info) {
2.   RUNTIME_CALL_TIMER_SCOPE_DISABLED_BY_DEFAULT(info.GetIsolate(), "Blink_FormData_keys");
3. BLINK_BINDINGS_TRACE_EVENT("FormData.keys");
5. v8::Isolate* isolate = info.GetIsolate();
6. v8::Local<v8::Object> v8_receiver = info.This();
7. FormData* blink_receiver = V8FormData::ToWrappableUnsafe(isolate, v8_receiver);
8. v8::Local<v8::Context> receiver_context = v8_receiver->GetCreationContextChecked();
9. ScriptState* receiver_script_state = ScriptState::From(receiver_context);
10. ScriptState* script_state = receiver_script_state;
11. const ExceptionContextType exception_context_type = ExceptionContextType::kOperationInvoke;
12. const char* const class_like_name = "FormData";
13. const char* const property_name = "keys";
14. ExceptionState exception_state(isolate, exception_context_type, class_like_name, property_name);
15. auto&& return_value = blink_receiver->keysForBinding(script_state, exception_state);
16. if (UNLIKELY(exception_state.HadException())) {
17.   return;
18. }
19. bindings::V8SetReturnValue(info, return_value, blink_receiver);
20. }
22. void ValuesOperationCallback(const v8::FunctionCallbackInfo<v8::Value>& info) {
23.   RUNTIME_CALL_TIMER_SCOPE_DISABLED_BY_DEFAULT(info.GetIsolate(), "Blink_FormData_values");
24. BLINK_BINDINGS_TRACE_EVENT("FormData.values");
27. v8::Isolate* isolate = info.GetIsolate();
28. v8::Local<v8::Object> v8_receiver = info.This();
29. FormData* blink_receiver = V8FormData::ToWrappableUnsafe(isolate, v8_receiver);
30. v8::Local<v8::Context> receiver_context = v8_receiver->GetCreationContextChecked();
31. ScriptState* receiver_script_state = ScriptState::From(receiver_context);
32. ScriptState* script_state = receiver_script_state;
33. const ExceptionContextType exception_context_type = ExceptionContextType::kOperationInvoke;
34. const char* const class_like_name = "FormData";
35. const char* const property_name = "values";
36. ExceptionState exception_state(isolate, exception_context_type, class_like_name, property_name);
37. auto&& return_value = blink_receiver->valuesForBinding(script_state, exception_state);
38. if (UNLIKELY(exception_state.HadException())) {
39.   return;
40. }
41. bindings::V8SetReturnValue(info, return_value, blink_receiver);
42. }

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2.5）、form submit 管理类FormSubmission

   网页点击submit会调用到FormSubmission。
third_party\blink\renderer\core\loader\form_submission.h
third_party\blink\renderer\core\loader\form_submission.cc

2. #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_LOADER_FORM_SUBMISSION_H_
3. #define THIRD_PARTY_BLINK_RENDERER_CORE_LOADER_FORM_SUBMISSION_H_
5. #include "third_party/blink/public/common/tokens/tokens.h"
6. #include "third_party/blink/public/mojom/frame/policy_container.mojom-blink.h"
7. #include "third_party/blink/public/mojom/frame/triggering_event_info.mojom-blink-forward.h"
8. #include "third_party/blink/public/web/web_frame_load_type.h"
9. #include "third_party/blink/renderer/core/loader/frame_loader_types.h"
10. #include "third_party/blink/renderer/core/loader/navigation_policy.h"
11. #include "third_party/blink/renderer/platform/heap/garbage_collected.h"
12. #include "third_party/blink/renderer/platform/weborigin/kurl.h"
13. #include "third_party/blink/renderer/platform/heap/member.h"
14. #include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
16. namespace blink {
18. class Element;
19. class EncodedFormData;
20. class Event;
21. class Frame;
22. class HTMLFormControlElement;
23. class HTMLFormElement;
24. class LocalDOMWindow;
25. class ResourceRequest;
26. class SourceLocation;
28. class FormSubmission final : public GarbageCollected<FormSubmission> {
29. public:
30.   enum SubmitMethod { kGetMethod, kPostMethod, kDialogMethod };
32.   class Attributes {
33.     DISALLOW_NEW();
35.    public:
36.     Attributes()
37.         : method_(kGetMethod),
38.           is_multi_part_form_(false),
39.           encoding_type_("application/x-www-form-urlencoded") {}
40.     Attributes(const Attributes&) = delete;
41.     Attributes& operator=(const Attributes&) = delete;
43.     SubmitMethod Method() const { return method_; }
44.     static SubmitMethod ParseMethodType(const String&);
45.     void UpdateMethodType(const String&);
46.     static String MethodString(SubmitMethod);
48.     const String& Action() const { return action_; }
49.     void ParseAction(const String&);
51.     const AtomicString& Target() const { return target_; }
52.     void SetTarget(const AtomicString& target) { target_ = target; }
54.     const AtomicString& EncodingType() const { return encoding_type_; }
55.     static AtomicString ParseEncodingType(const String&);
56.     void UpdateEncodingType(const String&);
57.     bool IsMultiPartForm() const { return is_multi_part_form_; }
59.     const String& AcceptCharset() const { return accept_charset_; }
60.     void SetAcceptCharset(const String& value) { accept_charset_ = value; }
62.     void CopyFrom(const Attributes&);
64.    private:
65.     SubmitMethod method_;
66.     bool is_multi_part_form_;
68.     String action_;
69.     AtomicString target_;
70.     AtomicString encoding_type_;
71.     String accept_charset_;
72.   };
74.   // Create FormSubmission
75.   //
76.   // This returns nullptr if form submission is not allowed for the given
77.   // arguments. For example, if navigation policy for the event is
78.   // `kNavigationPolicyLinkPreview`.
79.   static FormSubmission* Create(HTMLFormElement*,
80.                                 const Attributes&,
81.                                 const Event*,
82.                                 HTMLFormControlElement* submit_button);
84.   FormSubmission(
85.       SubmitMethod,
86.       const KURL& action,
87.       const AtomicString& target,
88.       const AtomicString& content_type,
89.       Element* submitter,
90.       scoped_refptr<EncodedFormData>,
91.       const Event*,
92.       NavigationPolicy navigation_policy,
93.       mojom::blink::TriggeringEventInfo triggering_event_info,
94.       ClientNavigationReason reason,
95.       std::unique_ptr<ResourceRequest> resource_request,
96.       Frame* target_frame,
97.       WebFrameLoadType load_type,
98.       LocalDOMWindow* origin_window,
99.       const LocalFrameToken& initiator_frame_token,
100.       std::unique_ptr<SourceLocation> source_location,
101.       mojo::PendingRemote<mojom::blink::PolicyContainerHostKeepAliveHandle>
102.           initiator_policy_container_keep_alive_handle);
103.   // FormSubmission for DialogMethod
104.   explicit FormSubmission(const String& result);
106.   void Trace(Visitor*) const;
108.   void Navigate();
110.   KURL RequestURL() const;
112.   SubmitMethod Method() const { return method_; }
113.   const KURL& Action() const { return action_; }
114.   EncodedFormData* Data() const { return form_data_.get(); }
116.   const String& Result() const { return result_; }
118.   Frame* TargetFrame() const { return target_frame_.Get(); }
120. private:
121.   // FIXME: Hold an instance of Attributes instead of individual members.
122.   SubmitMethod method_;
123.   KURL action_;
124.   AtomicString target_;
125.   AtomicString content_type_;
126.   Member<Element> submitter_;
127.   scoped_refptr<EncodedFormData> form_data_;
128.   NavigationPolicy navigation_policy_;
129.   mojom::blink::TriggeringEventInfo triggering_event_info_;
130.   String result_;
131.   ClientNavigationReason reason_;
132.   std::unique_ptr<ResourceRequest> resource_request_;
133.   Member<Frame> target_frame_;
134.   WebFrameLoadType load_type_;
135.   Member<LocalDOMWindow> origin_window_;
136.   LocalFrameToken initiator_frame_token_;
138.   // Since form submissions are scheduled asynchronously, we need to store the
139.   // source location when we create the form submission and then pass it over to
140.   // the `FrameLoadRequest`. Capturing the source location later when creating
141.   // the `FrameLoadRequest` will not return the correct location.
142.   std::unique_ptr<SourceLocation> source_location_;
144.   // Since form submissions are scheduled asynchronously, we need to keep a
145.   // handle to the initiator PolicyContainerHost. This ensures that it remains
146.   // available in the browser until we create the NavigationRequest.
147.   mojo::PendingRemote<mojom::blink::PolicyContainerHostKeepAliveHandle>
148.       initiator_policy_container_keep_alive_handle_;
149. };
151. }  // namespace blink
153. #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LOADER_FORM_SUBMISSION_H_

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2.6）、submit_input类对应前端<input type="submit"：

third_party\blink\renderer\core\html\forms\submit_input_type.h
third_party\blink\renderer\core\html\forms\submit_input_type.cc

2. #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_SUBMIT_INPUT_TYPE_H_
3. #define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_SUBMIT_INPUT_TYPE_H_
5. #include "third_party/blink/renderer/core/html/forms/base_button_input_type.h"
7. namespace blink {
9. class SubmitInputType final : public BaseButtonInputType {
10. public:
11.   explicit SubmitInputType(HTMLInputElement& element);
13. private:
14.   void AppendToFormData(FormData&) const override;
15.   bool SupportsRequired() const override;
16.   void HandleDOMActivateEvent(Event&) override;
17.   bool CanBeSuccessfulSubmitButton() override;
18.   String DefaultLabel() const override;
19.   bool IsTextButton() const override;
20.   void ValueAttributeChanged() override;
21. };
23. template <>
24. struct DowncastTraits<SubmitInputType> {
25.   static bool AllowFrom(const InputType& type) {
26.     return type.IsSubmitInputType();
27.   }
28. };
30. }  // namespace blink
32. #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_FORMS_SUBMIT_INPUT_TYPE_H_

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三、看下form表单提交过程：

form表单提交过程：
1、render历程点击提交<input type="submit" value="提交">
2、render历程在HTMLFormElement类中构建 FormSubmission并剖析<input>内容、从而构建出请求参数：FirstName=Mickey&LastName=Mouse 以及
获取method="get"
/*
First name: <input type="text" name="FirstName" value="Mickey"><br>
Last name: <input type="text" name="LastName" value="Mouse"><br>
*/
末了拼接出请求URL
https://www.runoob.com/try/demo_source/demo-form.php?FirstName=Mickey&LastName=Mouse
3、给主历程发送message.set_method_name("CreateNewWindow");
 在新标签中打开https://www.runoob.com/try/demo_source/demo-form.php?FirstName=Mickey&LastName=Mouse。

============================优雅的分割线===================================

1、render历程点击提交<input type="submit" value="提交">

   SubmitInputType::HandleDOMActivateEvent(Event& event)

1. void SubmitInputType::HandleDOMActivateEvent(Event& event) {
2.   if (GetElement().IsDisabledFormControl() || !GetElement().Form())
3.     return;
4.   // Event handlers can run.
5.   GetElement().Form()->PrepareForSubmission(&event, &GetElement());
6.   event.SetDefaultHandled();
7. }

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2、HTMLFormElement::ScheduleFormSubmission 函数

调用 FormSubmission* form_submission =
      FormSubmission::Create(this, attributes_, event, submit_button);

1. void HTMLFormElement::ScheduleFormSubmission(
2.     const Event* event,
3.     HTMLFormControlElement* submit_button) {
4.   LocalFrameView* view = GetDocument().View();
5.   LocalFrame* frame = GetDocument().GetFrame();
6.   if (!view || !frame || !frame->GetPage())
7.     return;
9.   // https://html.spec.whatwg.org/C/#form-submission-algorithm
10.   // 2. If form document is not connected, has no associated browsing context,
11.   // or its active sandboxing flag set has its sandboxed forms browsing
12.   // context flag set, then abort these steps without doing anything.
13.   if (!isConnected()) {
14.     GetDocument().AddConsoleMessage(MakeGarbageCollected<ConsoleMessage>(
15.         mojom::ConsoleMessageSource::kJavaScript,
16.         mojom::ConsoleMessageLevel::kWarning,
17.         "Form submission canceled because the form is not connected"));
18.     return;
19.   }
21.   if (is_constructing_entry_list_) {
22.     GetDocument().AddConsoleMessage(MakeGarbageCollected<ConsoleMessage>(
23.         mojom::ConsoleMessageSource::kJavaScript,
24.         mojom::ConsoleMessageLevel::kWarning,
25.         "Form submission canceled because the form is "
26.         "constructing entry list"));
27.     return;
28.   }
30.   if (is_submitting_)
31.     return;
33.   // Delay dispatching 'close' to dialog until done submitting.
34.   EventQueueScope scope_for_dialog_close;
35.   base::AutoReset<bool> submit_scope(&is_submitting_, true);
37.   if (event && !submit_button) {
38.     // In a case of implicit submission without a submit button, 'submit'
39.     // event handler might add a submit button. We search for a submit
40.     // button again.
41.     // TODO(tkent): Do we really need to activate such submit button?
42.     for (ListedElement* listed_element : ListedElements()) {
43.       auto* control = DynamicTo<HTMLFormControlElement>(listed_element);
44.       if (!control)
45.         continue;
46.       DCHECK(!control->IsActivatedSubmit());
47.       if (control->IsSuccessfulSubmitButton()) {
48.         submit_button = control;
49.         break;
50.       }
51.     }
52.   }
54.   FormSubmission* form_submission =
55.       FormSubmission::Create(this, attributes_, event, submit_button);
56.   if (!form_submission) {
57.     // Form submission is not allowed for some NavigationPolicies, e.g. Link
58.     // Preview. If an user triggered such user event for form submission, just
59.     // ignores it.
60.     return;
61.   }
62.   Frame* target_frame = form_submission->TargetFrame();
64.   // 'formdata' event handlers might disconnect the form.
65.   if (!isConnected()) {
66.     GetDocument().AddConsoleMessage(MakeGarbageCollected<ConsoleMessage>(
67.         mojom::ConsoleMessageSource::kJavaScript,
68.         mojom::ConsoleMessageLevel::kWarning,
69.         "Form submission canceled because the form is not connected"));
70.     return;
71.   }
73.   if (form_submission->Method() == FormSubmission::kDialogMethod) {
74.     SubmitDialog(form_submission);
75.     return;
76.   }
78.   DCHECK(form_submission->Method() == FormSubmission::kPostMethod ||
79.          form_submission->Method() == FormSubmission::kGetMethod);
80.   DCHECK(form_submission->Data());
81.   if (form_submission->Action().IsEmpty())
82.     return;
83.   if (GetExecutionContext()->IsSandboxed(
84.           network::mojom::blink::WebSandboxFlags::kForms)) {
85.     // FIXME: This message should be moved off the console once a solution to
86.     // https://bugs.webkit.org/show_bug.cgi?id=103274 exists.
87.     GetExecutionContext()->AddConsoleMessage(
88.         MakeGarbageCollected<ConsoleMessage>(
89.             mojom::blink::ConsoleMessageSource::kSecurity,
90.             mojom::blink::ConsoleMessageLevel::kError,
91.             "Blocked form submission to '" +
92.                 form_submission->Action().ElidedString() +
93.                 "' because the form's frame is sandboxed and the 'allow-forms' "
94.                 "permission is not set."));
95.     return;
96.   }
98.   if (form_submission->Action().ProtocolIsJavaScript()) {
99.     // For javascript URLs we need to do the CSP check for 'form-action' here.
100.     // All other schemes are checked in the browser.
101.     //
102.     // TODO(antoniosartori): Should we keep the 'form-action' check for
103.     // javascript: URLs? For 'frame-src' and 'navigate-to', we do not check
104.     // javascript: URLs. Reading the specification, it looks like 'form-action'
105.     // should not apply to javascript: URLs.
106.     if (!GetExecutionContext()->GetContentSecurityPolicy()->AllowFormAction(
107.             form_submission->Action())) {
108.       return;
109.     }
110.   }
112.   UseCounter::Count(GetDocument(), WebFeature::kFormsSubmitted);
113.   if (MixedContentChecker::IsMixedFormAction(GetDocument().GetFrame(),
114.                                              form_submission->Action())) {
115.     UseCounter::Count(GetDocument(), WebFeature::kMixedContentFormsSubmitted);
116.   }
117.   if (FastHasAttribute(html_names::kDisabledAttr)) {
118.     UseCounter::Count(GetDocument(),
119.                       WebFeature::kFormDisabledAttributePresentAndSubmit);
120.   }
122.   if (!target_frame)
123.     return;
125.   if (form_submission->Action().ProtocolIsJavaScript()) {
126.     // For javascript urls, don't post a task to execute the form submission
127.     // because we already get another task posted for it in
128.     // Document::ProcessJavascriptUrl. If we post two tasks, the javascript will
129.     // be run too late according to some tests.
130.     form_submission->Navigate();
131.     return;
132.   }
134.   FrameScheduler* scheduler = GetDocument().GetFrame()->GetFrameScheduler();
136.   if (auto* target_local_frame = DynamicTo<LocalFrame>(target_frame)) {
137.     if (!target_local_frame->IsNavigationAllowed())
138.       return;
140.     // Cancel parsing if the form submission is targeted at this frame.
141.     if (target_local_frame == GetDocument().GetFrame() &&
142.         !form_submission->Action().ProtocolIsJavaScript()) {
143.       target_local_frame->GetDocument()->CancelParsing();
144.     }
146.     // Use the target frame's frame scheduler. If we can't due to targeting a
147.     // RemoteFrame, then use the frame scheduler from the frame this form is in.
148.     scheduler = target_local_frame->GetFrameScheduler();
150.     // Cancel pending javascript url navigations for the target frame. This new
151.     // form submission should take precedence over them.
152.     target_local_frame->GetDocument()->CancelPendingJavaScriptUrls();
154.     // Cancel any pre-existing attempt to navigate the target frame which was
155.     // already sent to the browser process so this form submission will take
156.     // precedence over it.
157.     target_local_frame->Loader().CancelClientNavigation();
158.   }
160.   cancel_last_submission_ =
161.       target_frame->ScheduleFormSubmission(scheduler, form_submission);
162. }

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3、FormSubmission::Create（）函数构建FirstName=Mickey&LastName=Mouse，以及打开提交页面方式：

1. FormSubmission* FormSubmission::Create(HTMLFormElement* form,
2.                                        const Attributes& attributes,
3.                                        const Event* event,
4.                                        HTMLFormControlElement* submit_button) {
5.   DCHECK(form);
7.   FormSubmission::Attributes copied_attributes;
8.   copied_attributes.CopyFrom(attributes);
9.   if (submit_button) {
10.     AtomicString attribute_value;
11.     if (!(attribute_value =
12.               submit_button->FastGetAttribute(html_names::kFormactionAttr))
13.              .IsNull())
14.       copied_attributes.ParseAction(attribute_value);
15.     if (!(attribute_value =
16.               submit_button->FastGetAttribute(html_names::kFormenctypeAttr))
17.              .IsNull())
18.       copied_attributes.UpdateEncodingType(attribute_value);
19.     if (!(attribute_value =
20.               submit_button->FastGetAttribute(html_names::kFormmethodAttr))
21.              .IsNull())
22.       copied_attributes.UpdateMethodType(attribute_value);
23.     if (!(attribute_value =
24.               submit_button->FastGetAttribute(html_names::kFormtargetAttr))
25.              .IsNull())
26.       copied_attributes.SetTarget(attribute_value);
27.   }
29.   if (copied_attributes.Method() == kDialogMethod) {
30.     if (submit_button) {
31.       return MakeGarbageCollected<FormSubmission>(
32.           submit_button->ResultForDialogSubmit());
33.     }
34.     return MakeGarbageCollected<FormSubmission>("");
35.   }
37.   Document& document = form->GetDocument();
38.   KURL action_url = document.CompleteURL(copied_attributes.Action().empty()
39.                                              ? document.Url().GetString()
40.                                              : copied_attributes.Action());
42.   if ((document.domWindow()->GetSecurityContext().GetInsecureRequestPolicy() &
43.        mojom::blink::InsecureRequestPolicy::kUpgradeInsecureRequests) !=
44.           mojom::blink::InsecureRequestPolicy::kLeaveInsecureRequestsAlone &&
45.       action_url.ProtocolIs("http") &&
46.       !network::IsUrlPotentiallyTrustworthy(GURL(action_url))) {
47.     UseCounter::Count(document,
48.                       WebFeature::kUpgradeInsecureRequestsUpgradedRequestForm);
49.     action_url.SetProtocol("https");
50.     if (action_url.Port() == 80)
51.       action_url.SetPort(443);
52.   }
54.   bool is_mailto_form = action_url.ProtocolIs("mailto");
55.   bool is_multi_part_form = false;
56.   AtomicString encoding_type = copied_attributes.EncodingType();
58.   if (copied_attributes.Method() == kPostMethod) {
59.     is_multi_part_form = copied_attributes.IsMultiPartForm();
60.     if (is_multi_part_form && is_mailto_form) {
61.       encoding_type = AtomicString("application/x-www-form-urlencoded");
62.       is_multi_part_form = false;
63.     }
64.   }
65.   WTF::TextEncoding data_encoding =
66.       is_mailto_form
67.           ? UTF8Encoding()
68.           : FormDataEncoder::EncodingFromAcceptCharset(
69.                 copied_attributes.AcceptCharset(), document.Encoding());
70.   //解析<input>构建请求参数FirstName=Mickey&LastName=Mouse
71.   FormData* dom_form_data = form->ConstructEntryList(
72.       submit_button, data_encoding.EncodingForFormSubmission());
73.   DCHECK(dom_form_data);
75.   scoped_refptr<EncodedFormData> form_data;
76.   String boundary;
78.   if (is_multi_part_form) {
79.     form_data = dom_form_data->EncodeMultiPartFormData();
80.     boundary = form_data->Boundary().data();
81.   } else {
82.     form_data = dom_form_data->EncodeFormData(
83.         attributes.Method() == kGetMethod
84.             ? EncodedFormData::kFormURLEncoded
85.             : EncodedFormData::ParseEncodingType(encoding_type));
86.     if (copied_attributes.Method() == kPostMethod && is_mailto_form) {
87.       // Convert the form data into a string that we put into the URL.
88.       AppendMailtoPostFormDataToURL(action_url, *form_data, encoding_type);
89.       form_data = EncodedFormData::Create();
90.     }
91.   }
93.   form_data->SetIdentifier(GenerateFormDataIdentifier());
94.   form_data->SetContainsPasswordData(dom_form_data->ContainsPasswordData());
96.   if (copied_attributes.Method() != FormSubmission::kPostMethod &&
97.       !action_url.ProtocolIsJavaScript()) {
98.     action_url.SetQuery(form_data->FlattenToString());
99.   }
101.   std::unique_ptr<ResourceRequest> resource_request =
102.       std::make_unique<ResourceRequest>(action_url);
103.   ClientNavigationReason reason = ClientNavigationReason::kFormSubmissionGet;
104.   if (copied_attributes.Method() == FormSubmission::kPostMethod) {
105.     reason = ClientNavigationReason::kFormSubmissionPost;
106.     resource_request->SetHttpMethod(http_names::kPOST);
107.     resource_request->SetHttpBody(form_data);
109.     // construct some user headers if necessary
110.     if (boundary.empty()) {
111.       resource_request->SetHTTPContentType(encoding_type);
112.     } else {
113.       resource_request->SetHTTPContentType(encoding_type +
114.                                            "; boundary=" + boundary);
115.     }
116.   }
117.   resource_request->SetHasUserGesture(
118.       LocalFrame::HasTransientUserActivation(form->GetDocument().GetFrame()));
119.   resource_request->SetFormSubmission(true);
121.   mojom::blink::TriggeringEventInfo triggering_event_info;
122.   if (event) {
123.     triggering_event_info =
124.         event->isTrusted()
125.             ? mojom::blink::TriggeringEventInfo::kFromTrustedEvent
126.             : mojom::blink::TriggeringEventInfo::kFromUntrustedEvent;
127.     if (event->UnderlyingEvent())
128.       event = event->UnderlyingEvent();
129.   } else {
130.     triggering_event_info = mojom::blink::TriggeringEventInfo::kNotFromEvent;
131.   }
133.   FrameLoadRequest frame_request(form->GetDocument().domWindow(),
134.                                  *resource_request);
135.   //设置submit打开策略
136.   NavigationPolicy navigation_policy = NavigationPolicyFromEvent(event);
137.   if (navigation_policy == kNavigationPolicyLinkPreview) {
138.     return nullptr;
139.   }
140.   frame_request.SetNavigationPolicy(navigation_policy);
141.   frame_request.SetClientRedirectReason(reason);
142.   if (submit_button) {
143.     frame_request.SetSourceElement(submit_button);
144.   } else {
145.     frame_request.SetSourceElement(form);
146.   }
147.   frame_request.SetTriggeringEventInfo(triggering_event_info);
148.   AtomicString target_or_base_target = frame_request.CleanNavigationTarget(
149.       copied_attributes.Target().empty() ? document.BaseTarget()
150.                                          : copied_attributes.Target());
152.   if (form->HasRel(HTMLFormElement::kNoReferrer)) {
153.     frame_request.SetNoReferrer();
154.     frame_request.SetNoOpener();
155.   }
156.   if (form->HasRel(HTMLFormElement::kNoOpener) ||
157.       (EqualIgnoringASCIICase(target_or_base_target, "_blank") &&
158.        !form->HasRel(HTMLFormElement::kOpener) &&
159.        form->GetDocument()
160.            .domWindow()
161.            ->GetFrame()
162.            ->GetSettings()
163.            ->GetTargetBlankImpliesNoOpenerEnabledWillBeRemoved())) {
164.     frame_request.SetNoOpener();
165.   }
166.   //给主进程发送message.set_method_name("CreateNewWindow");
167.   Frame* target_frame =
168.       form->GetDocument()
169.           .GetFrame()
170.           ->Tree()
171.           .FindOrCreateFrameForNavigation(frame_request, target_or_base_target)
172.           .frame;
174.   // Apply replacement now, before any async steps, as the result may change.
175.   WebFrameLoadType load_type = WebFrameLoadType::kStandard;
176.   LocalFrame* target_local_frame = DynamicTo<LocalFrame>(target_frame);
177.   if (target_local_frame &&
178.       target_local_frame->NavigationShouldReplaceCurrentHistoryEntry(
179.           frame_request, load_type)) {
180.     load_type = WebFrameLoadType::kReplaceCurrentItem;
181.   }
183.   return MakeGarbageCollected<FormSubmission>(
184.       copied_attributes.Method(), action_url, target_or_base_target,
185.       encoding_type, frame_request.GetSourceElement(), std::move(form_data),
186.       event, frame_request.GetNavigationPolicy(), triggering_event_info, reason,
187.       std::move(resource_request), target_frame, load_type,
188.       form->GetDocument().domWindow(),
189.       form->GetDocument().GetFrame()->GetLocalFrameToken(),
190.       CaptureSourceLocation(form->GetDocument().domWindow()),
191.       form->GetDocument()
192.           .domWindow()
193.           ->GetPolicyContainer()
194.           ->IssueKeepAliveHandle());
195. }

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 3.1）、构建FirstName=Mickey&LastName=Mouse 参数

/ /ConstructEntryList函数遍历form表单位素
  FormData* dom_form_data = form->ConstructEntryList(
      submit_button, data_encoding.EncodingForFormSubmission());
  DCHECK(dom_form_data);
3.2）、FormSubmission::Create调用FindOrCreateFrameForNavigation

用来打开提交新页面。
  Frame* target_frame =
      form->GetDocument()
          .GetFrame()
          ->Tree()
          .FindOrCreateFrameForNavigation(frame_request, target_or_base_target)
          .frame;

3.3）、FindOrCreateFrameForNavigation调用RenderFrameImpl::CreateNewWindow 函数

RenderFrameImpl::CreateNewWindow函数定义（content\renderer\render_frame_impl.cc）：

1. WebView* RenderFrameImpl::CreateNewWindow(
2.     const WebURLRequest& request,
3.     const blink::WebWindowFeatures& features,
4.     const WebString& frame_name,
5.     WebNavigationPolicy policy,
6.     network::mojom::WebSandboxFlags sandbox_flags,
7.     const blink::SessionStorageNamespaceId& session_storage_namespace_id,
8.     bool& consumed_user_gesture,
9.     const absl::optional<blink::Impression>& impression,
10.     const absl::optional<blink::WebPictureInPictureWindowOptions>& pip_options,
11.     const blink::WebURL& base_url) {
12.   consumed_user_gesture = false;
13.   mojom::CreateNewWindowParamsPtr params = mojom::CreateNewWindowParams::New();
15.   // The user activation check is done at the browser process through
16.   // |frame_host->CreateNewWindow()| call below.  But the extensions case
17.   // handled through the following |if| is an exception.
18.   params->allow_popup = false;
19.   if (GetContentClient()->renderer()->AllowPopup())
20.     params->allow_popup = true;
22.   params->window_container_type = WindowFeaturesToContainerType(features);
24.   params->session_storage_namespace_id = session_storage_namespace_id;
25.   if (!features.noopener) {
26.     params->clone_from_session_storage_namespace_id =
27.         GetWebView()->GetSessionStorageNamespaceId();
28.   }
30.   const std::string& frame_name_utf8 = frame_name.Utf8(
31.       WebString::UTF8ConversionMode::kStrictReplacingErrorsWithFFFD);
32.   params->frame_name = frame_name_utf8;
33.   params->opener_suppressed = features.noopener;
34.   params->disposition = NavigationPolicyToDisposition(policy);
35.   if (!request.IsNull()) {
36.     params->target_url = request.Url();
37.     // The browser process does not consider empty URLs as valid (partly due to
38.     // a risk of treating them as a navigation to the privileged NTP in some
39.     // cases), so treat an attempt to create a window with an empty URL as
40.     // opening about:blank.
41.     //
42.     // Similarly, javascript: URLs should not be sent to the browser process,
43.     // since they are either handled within the renderer process (if a window is
44.     // created within the same browsing context group) or ignored (in the
45.     // noopener case). Use about:blank for the URL in that case as well, to
46.     // reduce the risk of running them incorrectly.
47.     if (params->target_url.is_empty() ||
48.         params->target_url.SchemeIs(url::kJavaScriptScheme)) {
49.       params->target_url = GURL(url::kAboutBlankURL);
50.     }
52.     params->referrer = blink::mojom::Referrer::New(
53.         blink::WebStringToGURL(request.ReferrerString()),
54.         request.GetReferrerPolicy());
55.   }
56.   params->features = ConvertWebWindowFeaturesToMojoWindowFeatures(features);
58.   params->is_form_submission = request.IsFormSubmission();
59.   params->form_submission_post_data =
60.       blink::GetRequestBodyForWebURLRequest(request);
61.   params->form_submission_post_content_type = request.HttpContentType().Utf8();
63.   params->impression = impression;
65.   if (pip_options) {
66.     CHECK_EQ(policy, blink::kWebNavigationPolicyPictureInPicture);
67.     auto pip_mojom_opts = blink::mojom::PictureInPictureWindowOptions::New();
68.     pip_mojom_opts->width = pip_options->width;
69.     pip_mojom_opts->height = pip_options->height;
70.     // TODO(crbug.com/1444658): Remove this from mojom and the browser side.
71.     pip_mojom_opts->initial_aspect_ratio = 0.0;
72.     // TODO(crbug.com/1410379): Remove this from mojom and the browser side.
73.     pip_mojom_opts->lock_aspect_ratio = false;
74.     params->pip_options = std::move(pip_mojom_opts);
75.   }
77.   params->download_policy.ApplyDownloadFramePolicy(
78.       /*is_opener_navigation=*/false, request.HasUserGesture(),
79.       // `openee_can_access_opener_origin` only matters for opener navigations,
80.       // so its value here is irrelevant.
81.       /*openee_can_access_opener_origin=*/true,
82.       !GetWebFrame()->IsAllowedToDownload(), GetWebFrame()->IsAdFrame());
84.   params->initiator_activation_and_ad_status =
85.       blink::GetNavigationInitiatorActivationAndAdStatus(
86.           request.HasUserGesture(), GetWebFrame()->IsAdFrame(),
87.           GetWebFrame()->IsAdScriptInStack());
89.   // We preserve this information before sending the message since |params| is
90.   // moved on send.
91.   bool is_background_tab =
92.       params->disposition == WindowOpenDisposition::NEW_BACKGROUND_TAB;
94.   mojom::CreateNewWindowStatus status;
95.   mojom::CreateNewWindowReplyPtr reply;
96.   auto* frame_host = GetFrameHost();
97.   if (!frame_host->CreateNewWindow(std::move(params), &status, &reply)) {
98.     // The sync IPC failed, e.g. maybe the render process is in the middle of
99.     // shutting down. Can't create a new window without the browser process,
100.     // so just bail out.
101.     return nullptr;
102.   }
104.   // If creation of the window was blocked (e.g. because this frame doesn't
105.   // have user activation), return before consuming user activation. A frame
106.   // that isn't allowed to open a window  shouldn't be able to consume the
107.   // activation for the rest of the frame tree.
108.   if (status == mojom::CreateNewWindowStatus::kBlocked)
109.     return nullptr;
111.   // For Android WebView, we support a pop-up like behavior for window.open()
112.   // even if the embedding app doesn't support multiple windows. In this case,
113.   // window.open() will return "window" and navigate it to whatever URL was
114.   // passed. We also don't need to consume user gestures to protect against
115.   // multiple windows being opened, because, well, the app doesn't support
116.   // multiple windows.
117.   // TODO(dcheng): It's awkward that this is plumbed into Blink but not really
118.   // used much in Blink, except to enable web testing... perhaps this should
119.   // be checked directly in the browser side.
120.   if (status == mojom::CreateNewWindowStatus::kReuse) {
121.     // In this case, treat javascript: URLs as blocked rather than running them
122.     // in a reused main frame in Android WebView. See https://crbug.com/1083819.
123.     if (!request.IsNull() && request.Url().ProtocolIs(url::kJavaScriptScheme)) {
124.       return nullptr;
125.     }
126.     return GetWebView();
127.   }
129.   // Consume the transient user activation in the current renderer.
130.   consumed_user_gesture = GetWebFrame()->ConsumeTransientUserActivation(
131.       blink::UserActivationUpdateSource::kBrowser);
133.   // If we should ignore the new window (e.g. because of `noopener`), return
134.   // now that user activation was consumed.
135.   if (status == mojom::CreateNewWindowStatus::kIgnore)
136.     return nullptr;
138.   DCHECK(reply);
139.   DCHECK_NE(MSG_ROUTING_NONE, reply->main_frame_route_id);
140.   DCHECK_NE(MSG_ROUTING_NONE, reply->widget_params->routing_id);
142.   // While this view may be a background extension page, it can spawn a visible
143.   // render view. So we just assume that the new one is not another background
144.   // page instead of passing on our own value.
145.   // TODO(vangelis): Can we tell if the new view will be a background page?
146.   bool never_composited = false;
148.   // The initial hidden state for the RenderViewImpl here has to match what the
149.   // browser will eventually decide for the given disposition. Since we have to
150.   // return from this call synchronously, we just have to make our best guess
151.   // and rely on the browser sending a WasHidden / WasShown message if it
152.   // disagrees.
153.   mojom::CreateViewParamsPtr view_params = mojom::CreateViewParams::New();
155.   view_params->opener_frame_token = GetWebFrame()->GetFrameToken();
156.   view_params->window_was_opened_by_another_window = true;
157.   view_params->renderer_preferences = GetWebView()->GetRendererPreferences();
158.   view_params->web_preferences = GetWebView()->GetWebPreferences();
160.   view_params->replication_state = blink::mojom::FrameReplicationState::New();
161.   view_params->replication_state->frame_policy.sandbox_flags = sandbox_flags;
162.   view_params->replication_state->name = frame_name_utf8;
163.   view_params->devtools_main_frame_token = reply->devtools_main_frame_token;
164.   view_params->browsing_context_group_info = reply->browsing_context_group_info;
165.   view_params->color_provider_colors = reply->color_provider_colors;
167.   auto main_frame_params = mojom::CreateLocalMainFrameParams::New();
168.   main_frame_params->frame_token = reply->main_frame_token;
169.   main_frame_params->routing_id = reply->main_frame_route_id;
170.   main_frame_params->frame = std::move(reply->frame);
171.   main_frame_params->interface_broker =
172.       std::move(reply->main_frame_interface_broker);
173.   main_frame_params->document_token = reply->document_token;
174.   main_frame_params->policy_container = std::move(reply->policy_container);
175.   main_frame_params->associated_interface_provider_remote =
176.       std::move(reply->associated_interface_provider);
177.   main_frame_params->widget_params = std::move(reply->widget_params);
178.   main_frame_params->subresource_loader_factories =
179.       base::WrapUnique(static_cast<blink::PendingURLLoaderFactoryBundle*>(
180.           CloneLoaderFactories()->Clone().release()));
182.   view_params->main_frame =
183.       mojom::CreateMainFrameUnion::NewLocalParams(std::move(main_frame_params));
184.   view_params->blink_page_broadcast = std::move(reply->page_broadcast);
185.   view_params->session_storage_namespace_id =
186.       reply->cloned_session_storage_namespace_id;
187.   DCHECK(!view_params->session_storage_namespace_id.empty())
188.       << "Session storage namespace must be populated.";
189.   view_params->hidden = is_background_tab;
190.   view_params->never_composited = never_composited;
192.   WebView* web_view = agent_scheduling_group_->CreateWebView(
193.       std::move(view_params),
194.       /*was_created_by_renderer=*/true, base_url);
196.   if (reply->wait_for_debugger) {
197.     blink::WebFrameWidget* frame_widget =
198.         web_view->MainFrame()->ToWebLocalFrame()->LocalRoot()->FrameWidget();
199.     frame_widget->WaitForDebuggerWhenShown();
200.   }
202.   return web_view;
203. }

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堆栈图：

1. @3        content.dll!content::RenderFrameImpl::CreateNewWindow(const blink::WebURLRequest & request, const blink::WebWindowFeatures & features, const blink::WebString & frame_name, blink::WebNavigationPolicy policy, network::mojom::WebSandboxFlags sandbox_flags, const std::__Cr::basic_string<char,std::__Cr::char_traits<char>,std::__Cr::allocator<char>> & session_storage_namespace_id, bool & consumed_user_gesture, const std::__Cr::optional<blink::Impression> & impression, const std::__Cr::optional<blink::WebPictureInPictureWindowOptions> & pip_options, const blink::WebURL & base_url) 行 6562        C++        已加载符号。
3. @2         blink_core.dll!blink::ChromeClientImpl::CreateWindowDelegate(blink::LocalFrame * frame, const blink::FrameLoadRequest & r, const WTF::AtomicString & name, const blink::WebWindowFeatures & features, network::mojom::WebSandboxFlags sandbox_flags, const std::__Cr::basic_string<char,std::__Cr::char_traits<char>,std::__Cr::allocator<char>> & session_storage_namespace_id, bool & consumed_user_gesture) 行 342        C++        已加载符号。
5. @1        blink_core.dll!blink::ChromeClient::CreateWindow(blink::LocalFrame * frame, const blink::FrameLoadRequest & r, const WTF::AtomicString & frame_name, const blink::WebWindowFeatures & features, network::mojom::WebSandboxFlags sandbox_flags, const std::__Cr::basic_string<char,std::__Cr::char_traits<char>,std::__Cr::allocator<char>> & session_storage_namespace_id, bool & consumed_user_gesture) 行 88        C++        已加载符号。
7. @0        blink_core.dll!blink::CreateNewWindow(blink::LocalFrame & opener_frame, blink::FrameLoadRequest & request, const WTF::AtomicString & frame_name) 行 355        C++        已加载符号。
8. >        blink_core.dll!blink::FrameTree::FindOrCreateFrameForNavigation(blink::FrameLoadRequest & request, const WTF::AtomicString & name) 行 217        C++        已加载符号。

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3.4）、RenderFrameImpl::CreateNewWindow 调用frame_host->CreateNewWindow 给主历程发送CreateNewWindow的mojom消息。

  mojom::CreateNewWindowStatus status;
  mojom::CreateNewWindowReplyPtr reply;
  auto* frame_host = GetFrameHost();
 //给主历程发送CreateNewWindow mojom消息
  if (!frame_host->CreateNewWindow(std::move(params), &status, &reply)) {
    // The sync IPC failed, e.g. maybe the render process is in the middle of
    // shutting down. Can't create a new window without the browser process,
    // so just bail out.
    return nullptr;
  }

4、主历程收到子历程发送的mojom CreateNewWindow消息：

在RenderFrameHostImpl::CreateNewWindow函数内里处理打开 submit提交URL="https://www.runoob.com/try/demo_source/demo-form.php?FirstName=Mickey&LastName=Mouse"
 src\content\browser\renderer_host\render_frame_host_impl.cc
浏览器打开了一个submit提交的新标签，至此form提交完成。

1. void RenderFrameHostImpl::CreateNewWindow(
2.     mojom::CreateNewWindowParamsPtr params,
3.     CreateNewWindowCallback callback) {
4.   DCHECK_CURRENTLY_ON(BrowserThread::UI);
5.   TRACE_EVENT2("navigation", "RenderFrameHostImpl::CreateNewWindow",
6.                "render_frame_host", this, "url", params->target_url);
8.   // Only top-most frames can open picture-in-picture windows.
9.   if (params->disposition == WindowOpenDisposition::NEW_PICTURE_IN_PICTURE &&
10.       GetParentOrOuterDocumentOrEmbedder()) {
11.     frame_host_associated_receiver_.ReportBadMessage(
12.         "Only top-most frames can open picture-in-picture windows.");
13.     return;
14.   }
16.   bool no_javascript_access = false;
18.   // Filter out URLs to which navigation is disallowed from this context.
19.   GetProcess()->FilterURL(false, &params->target_url);
21.   bool effective_transient_activation_state =
22.       params->allow_popup || HasTransientUserActivation() ||
23.       (transient_allow_popup_.IsActive() &&
24.        params->disposition == WindowOpenDisposition::NEW_POPUP);
26.   // Ignore window creation when sent from a frame that's not active or
27.   // created.
28.   bool can_create_window =
29.       IsActive() && is_render_frame_created() &&
30.       GetContentClient()->browser()->CanCreateWindow(
31.           this, GetLastCommittedURL(),
32.           GetOutermostMainFrame()->GetLastCommittedURL(),
33.           last_committed_origin_, params->window_container_type,
34.           params->target_url, params->referrer.To<Referrer>(),
35.           params->frame_name, params->disposition, *params->features,
36.           effective_transient_activation_state, params->opener_suppressed,
37.           &no_javascript_access);
39.   // If this frame isn't allowed to create a window, return early (before we
40.   // consume transient user activation).
41.   if (!can_create_window) {
42.     std::move(callback).Run(mojom::CreateNewWindowStatus::kBlocked, nullptr);
43.     return;
44.   }
46.   // Otherwise, consume user activation before we proceed. In particular, it is
47.   // important to do this before we return from the |opener_suppressed| case
48.   // below.
49.   // NB: This call will consume activations in the browser and the remote frame
50.   // proxies for this frame. The initiating renderer will consume its view of
51.   // the activations after we return.
53.   // See `owner_` invariants about `IsActive()`, which is implied by
54.   // `can_create_window`.
55.   CHECK(owner_);
56.   bool was_consumed = owner_->UpdateUserActivationState(
57.       blink::mojom::UserActivationUpdateType::kConsumeTransientActivation,
58.       blink::mojom::UserActivationNotificationType::kNone);
60.   // For Android WebView, we support a pop-up like behavior for window.open()
61.   // even if the embedding app doesn't support multiple windows. In this case,
62.   // window.open() will return "window" and navigate it to whatever URL was
63.   // passed.
64.   if (!GetOrCreateWebPreferences().supports_multiple_windows) {
65.     std::move(callback).Run(mojom::CreateNewWindowStatus::kReuse, nullptr);
66.     return;
67.   }
69.   // This will clone the sessionStorage for namespace_id_to_clone.
70.   StoragePartition* storage_partition = GetStoragePartition();
71.   DOMStorageContextWrapper* dom_storage_context =
72.       static_cast<DOMStorageContextWrapper*>(
73.           storage_partition->GetDOMStorageContext());
75.   scoped_refptr<SessionStorageNamespaceImpl> cloned_namespace;
76.   if (!params->clone_from_session_storage_namespace_id.empty()) {
77.     cloned_namespace = SessionStorageNamespaceImpl::CloneFrom(
78.         dom_storage_context, params->session_storage_namespace_id,
79.         params->clone_from_session_storage_namespace_id);
80.   } else {
81.     cloned_namespace = SessionStorageNamespaceImpl::Create(
82.         dom_storage_context, params->session_storage_namespace_id);
83.   }
85.   if (IsCredentialless() || IsNestedWithinFencedFrame() ||
86.       CoopSuppressOpener(/*opener=*/this)) {
87.     params->opener_suppressed = true;
88.     // TODO(https://crbug.com/1060691) This should be applied to all
89.     // popups opened with noopener.
90.     params->frame_name.clear();
91.   }
93.   RenderFrameHostImpl* top_level_opener = GetMainFrame();
94.   int popup_virtual_browsing_context_group =
95.       params->opener_suppressed
96.           ? CrossOriginOpenerPolicyAccessReportManager::
97.                 GetNewVirtualBrowsingContextGroup()
98.           : top_level_opener->virtual_browsing_context_group();
99.   int popup_soap_by_default_virtual_browsing_context_group =
100.       params->opener_suppressed
101.           ? CrossOriginOpenerPolicyAccessReportManager::
102.                 GetNewVirtualBrowsingContextGroup()
103.           : top_level_opener->soap_by_default_virtual_browsing_context_group();
105.   // If the opener is suppressed or script access is disallowed, we should
106.   // open the window in a new BrowsingInstance, and thus a new process. That
107.   // means the current renderer process will not be able to route messages to
108.   // it. Because of this, we will immediately show and navigate the window
109.   // in OnCreateNewWindowOnUI, using the params provided here.
110.   bool is_new_browsing_instance =
111.       params->opener_suppressed || no_javascript_access;
113.   DCHECK(IsRenderFrameLive());
115.   // The non-owning pointer |new_frame_tree| is valid in this stack frame since
116.   // nothing can delete it until this thread is freed up again.
117.   FrameTree* new_frame_tree =
118.       delegate_->CreateNewWindow(this, *params, is_new_browsing_instance,
119.                                  was_consumed, cloned_namespace.get());
121.   transient_allow_popup_.Deactivate();
123.   MaybeRecordAdClickMainFrameNavigationUseCounter(
124.       /*initiator_frame=*/this, params->initiator_activation_and_ad_status);
126.   if (is_new_browsing_instance || !new_frame_tree) {
127.     // Opener suppressed, Javascript access disabled, or delegate did not
128.     // provide a handle to any windows it created. In these cases, never tell
129.     // the renderer about the new window.
130.     std::move(callback).Run(mojom::CreateNewWindowStatus::kIgnore, nullptr);
131.     return;
132.   }
134.   DCHECK(!params->opener_suppressed);
136.   RenderFrameHostImpl* new_main_rfh =
137.       new_frame_tree->root()->current_frame_host();
139.   new_main_rfh->virtual_browsing_context_group_ =
140.       popup_virtual_browsing_context_group;
141.   new_main_rfh->soap_by_default_virtual_browsing_context_group_ =
142.       popup_soap_by_default_virtual_browsing_context_group;
144.   // COOP and COOP reporter are inherited from the opener to the popup's initial
145.   // empty document.
146.   if (IsOpenerSameOriginFrame(/*opener=*/this) &&
147.       GetMainFrame()->coop_access_report_manager()->coop_reporter()) {
148.     new_main_rfh->SetCrossOriginOpenerPolicyReporter(
149.         std::make_unique<CrossOriginOpenerPolicyReporter>(
150.             GetProcess()->GetStoragePartition(), GetLastCommittedURL(),
151.             params->referrer->url,
152.             // TODO(https://crbug.com/1385827): See if we need to send the
153.             // origin to reporters as well.
154.             new_main_rfh->cross_origin_opener_policy(), GetReportingSource(),
155.             isolation_info_.network_anonymization_key()));
156.   }
158.   mojo::PendingAssociatedRemote<mojom::Frame> pending_frame_remote;
159.   mojo::PendingAssociatedReceiver<mojom::Frame> pending_frame_receiver =
160.       pending_frame_remote.InitWithNewEndpointAndPassReceiver();
161.   new_main_rfh->SetMojomFrameRemote(std::move(pending_frame_remote));
163.   mojo::PendingRemote<blink::mojom::BrowserInterfaceBroker>
164.       browser_interface_broker;
165.   new_main_rfh->BindBrowserInterfaceBrokerReceiver(
166.       browser_interface_broker.InitWithNewPipeAndPassReceiver());
168.   mojo::PendingAssociatedRemote<blink::mojom::AssociatedInterfaceProvider>
169.       pending_associated_interface_provider;
170.   new_main_rfh->BindAssociatedInterfaceProviderReceiver(
171.       pending_associated_interface_provider
172.           .InitWithNewEndpointAndPassReceiver());
174.   // With this path, RenderViewHostImpl::CreateRenderView is never called
175.   // because `blink::WebView` is already created on the renderer side. Thus we
176.   // need to establish the connection here.
177.   mojo::PendingAssociatedRemote<blink::mojom::PageBroadcast> page_broadcast;
178.   mojo::PendingAssociatedReceiver<blink::mojom::PageBroadcast>
179.       page_broadcast_receiver =
180.           page_broadcast.InitWithNewEndpointAndPassReceiver();
182.   auto widget_params =
183.       new_main_rfh->GetLocalRenderWidgetHost()
184.           ->BindAndGenerateCreateFrameWidgetParamsForNewWindow();
186.   new_main_rfh->render_view_host()->BindPageBroadcast(
187.       std::move(page_broadcast));
189.   bool wait_for_debugger =
190.       devtools_instrumentation::ShouldWaitForDebuggerInWindowOpen();
192.   mojom::CreateNewWindowReplyPtr reply = mojom::CreateNewWindowReply::New(
193.       new_main_rfh->GetFrameToken(), new_main_rfh->GetRoutingID(),
194.       std::move(pending_frame_receiver), std::move(widget_params),
195.       std::move(page_broadcast_receiver), std::move(browser_interface_broker),
196.       std::move(pending_associated_interface_provider), cloned_namespace->id(),
197.       new_main_rfh->GetDevToolsFrameToken(), wait_for_debugger,
198.       new_main_rfh->GetDocumentToken(),
199.       new_main_rfh->policy_container_host()->CreatePolicyContainerForBlink(),
200.       blink::BrowsingContextGroupInfo(
201.           new_main_rfh->GetSiteInstance()->browsing_instance_token(),
202.           new_main_rfh->GetSiteInstance()->coop_related_group_token()),
203.       delegate_->GetColorProviderColorMaps());
205.   std::move(callback).Run(mojom::CreateNewWindowStatus::kSuccess,
206.                           std::move(reply));
208.   // The mojom reply callback with kSuccess causes the renderer to create the
209.   // renderer-side objects.
210.   new_main_rfh->render_view_host()->RenderViewCreated(new_main_rfh);
211. }

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子历程发送消息定义在
F:\code\google\src\out\Debug\gen\content\common\frame.mojom.cc
message.set_method_name("CreateNewWindow");

1. FrameHostProxy::FrameHostProxy(mojo::MessageReceiverWithResponder* receiver)
2.     : receiver_(receiver) {
3. }
4. bool FrameHostProxy::CreateNewWindow(
5.     CreateNewWindowParamsPtr param_params, CreateNewWindowStatus* out_param_status, CreateNewWindowReplyPtr* out_param_reply) {
6. #if BUILDFLAG(MOJO_TRACE_ENABLED)
7.   TRACE_EVENT_BEGIN1(
8.     "mojom", "Call content::mojom::FrameHost::CreateNewWindow (sync)", "input_parameters",
9.     [&](perfetto::TracedValue context){
10.       auto dict = std::move(context).WriteDictionary();
11.       perfetto::WriteIntoTracedValueWithFallback(
12.            dict.AddItem("params"), param_params,
13.                         "<value of type CreateNewWindowParamsPtr>");
14.    });
15. #else
16.   TRACE_EVENT0("mojom", "FrameHost::CreateNewWindow");
17. #endif
18.   
19.   const bool kExpectsResponse = true;
20.   const bool kIsSync = true;
21.   const bool kAllowInterrupt =
22.       true;
23.   const bool is_urgent = false;
24.   
25.   const uint32_t kFlags =
26.       ((kExpectsResponse) ? mojo::Message::kFlagExpectsResponse : 0) |
27.       ((kIsSync) ? mojo::Message::kFlagIsSync : 0) |
28.       ((kAllowInterrupt) ? 0 : mojo::Message::kFlagNoInterrupt) |
29.       ((is_urgent) ? mojo::Message::kFlagIsUrgent : 0);
30.   
31.   mojo::Message message(
32.       internal::kFrameHost_CreateNewWindow_Name, kFlags, 0, 0, nullptr);
33.   mojo::internal::MessageFragment<
34.       ::content::mojom::internal::FrameHost_CreateNewWindow_Params_Data> params(
35.           message);
36.   params.Allocate();
37.   mojo::internal::MessageFragment<
38.       typename decltype(params->params)::BaseType> params_fragment(
39.           params.message());
40.   mojo::internal::Serialize<::content::mojom::CreateNewWindowParamsDataView>(
41.       param_params, params_fragment);
42.   params->params.Set(
43.       params_fragment.is_null() ? nullptr : params_fragment.data());
44.   MOJO_INTERNAL_DLOG_SERIALIZATION_WARNING(
45.       params->params.is_null(),
46.       mojo::internal::VALIDATION_ERROR_UNEXPECTED_NULL_POINTER,
47.       "null params in FrameHost.CreateNewWindow request");
49. #if defined(ENABLE_IPC_FUZZER)
50.   message.set_interface_name(FrameHost::Name_);
51.   message.set_method_name("CreateNewWindow");
52. #endif
54.   bool result = false;
55.   std::unique_ptr<mojo::MessageReceiver> responder(
56.       new FrameHost_CreateNewWindow_HandleSyncResponse(
57.           &result, out_param_status, out_param_reply));
58.   ::mojo::internal::SendMojoMessage(*receiver_, message, std::move(responder));
59. #if BUILDFLAG(MOJO_TRACE_ENABLED)
60.   TRACE_EVENT_END1(
61.     "mojom", "FrameHost::CreateNewWindow", "sync_response_parameters",
62.     [&](perfetto::TracedValue context){
63.       auto dict = std::move(context).WriteDictionary();
64.       perfetto::WriteIntoTracedValueWithFallback(
65.            dict.AddItem("status"), out_param_status,
66.                         "<value of type CreateNewWindowStatus>");
67.       perfetto::WriteIntoTracedValueWithFallback(
68.            dict.AddItem("reply"), out_param_reply,
69.                         "<value of type CreateNewWindowReplyPtr>");
70.    });
71. #endif
72.   return result;
73. }

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总结：至此分析完毕。


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