[Bindings] Create and use V8 context snapshots

third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 41 matching lines @@
 
 typedef WTF::Vector<DOMDataStore*> DOMDataStoreList;
 
 // Used to hold data that is associated with a single v8::Isolate object, and
 // has a 1:1 relationship with v8::Isolate.
 class PLATFORM_EXPORT V8PerIsolateData {
   USING_FAST_MALLOC(V8PerIsolateData);
   WTF_MAKE_NONCOPYABLE(V8PerIsolateData);
 
  public:
+  enum class V8ContextMode {
+    kTakeSnapshot,
+    kDontUseSnapshot,
+    kUseSnapshot,
+  };
+
   class EndOfScopeTask {
     USING_FAST_MALLOC(EndOfScopeTask);
 
    public:
     virtual ~EndOfScopeTask() {}
     virtual void Run() = 0;
   };
 
   // Disables the UseCounter.
   // UseCounter depends on the current context, but it's not available during
@@ skipping 21 matching lines @@
   };
 
   // Use this class to abstract away types of members that are pointers to core/
   // objects, which are simply owned and released by V8PerIsolateData (see
   // m_threadDebugger for an example).
   class PLATFORM_EXPORT Data {
    public:
     virtual ~Data() = default;
   };
 
-  static v8::Isolate* Initialize(WebTaskRunner*);
+  static v8::Isolate* Initialize(WebTaskRunner*,
+                                 intptr_t* refernce_table,
+                                 V8ContextMode);
 
   static V8PerIsolateData* From(v8::Isolate* isolate) {
     DCHECK(isolate);
     DCHECK(isolate->GetData(gin::kEmbedderBlink));
     return static_cast<V8PerIsolateData*>(
         isolate->GetData(gin::kEmbedderBlink));
   }
 
   static void WillBeDestroyed(v8::Isolate*);
   static void Destroy(v8::Isolate*);
   static v8::Isolate* MainThreadIsolate();
 
   static void EnableIdleTasks(v8::Isolate*,
                               std::unique_ptr<gin::V8IdleTaskRunner>);
 
   v8::Isolate* GetIsolate() { return isolate_holder_.isolate(); }
+  v8::SnapshotCreator* GetSnapshotCreator() { return snapshot_creator_.get(); }
 
   StringCache* GetStringCache() { return string_cache_.get(); }
 
   bool IsHandlingRecursionLevelError() const {
     return is_handling_recursion_level_error_;
   }
   void SetIsHandlingRecursionLevelError(bool value) {
     is_handling_recursion_level_error_ = value;
   }
 
   bool IsReportingException() const { return is_reporting_exception_; }
   void SetReportingException(bool value) { is_reporting_exception_ = value; }
 
   bool IsUseCounterDisabled() const { return use_counter_disabled_; }
 
   V8PrivateProperty* PrivateProperty() { return private_property_.get(); }
 
   // Accessors to the cache of interface templates.
   v8::Local<v8::FunctionTemplate> FindInterfaceTemplate(const DOMWrapperWorld&,
                                                         const void* key);
   void SetInterfaceTemplate(const DOMWrapperWorld&,
                             const void* key,
                             v8::Local<v8::FunctionTemplate>);
+  void ClearPersistents();

[Yuki, 2017/05/30 14:35:58]

Add a comment what this function does (and why we need this).
This member function is public: but it's not expected to be used widely. 
Explicitly describe who are expected to call this function.

Maybe, ClearPersistentsForV8Snapshot would be a better name.

[peria, 2017/06/01 08:33:34]

Done.

+  V8ContextMode GetV8ContextMode() const { return v8_context_mode_; }

[Yuki, 2017/05/30 14:35:58]

GetV8ContextMode() seems relevant to GetSnapshotCreator().
Why are they put apart?

[peria, 2017/06/01 08:33:34]

Done.

 
   // Accessor to the cache of cross-origin accessible operation's templates.
   // Created templates get automatically cached.
   v8::Local<v8::FunctionTemplate> FindOrCreateOperationTemplate(
       const DOMWrapperWorld&,
       const void* key,
       v8::FunctionCallback,
       v8::Local<v8::Value> data,
       v8::Local<v8::Signature>,
       int length);
@@ skipping 61 matching lines @@
 
   void SetScriptWrappableVisitor(
       std::unique_ptr<ScriptWrappableVisitor> visitor) {
     script_wrappable_visitor_ = std::move(visitor);
   }
   ScriptWrappableVisitor* GetScriptWrappableVisitor() {
     return script_wrappable_visitor_.get();
   }
 
  private:
-  explicit V8PerIsolateData(WebTaskRunner*);
+  V8PerIsolateData(WebTaskRunner*, intptr_t* reference_table, V8ContextMode);
+  // To create with v8::SnapshotCreator.
+  V8PerIsolateData(intptr_t* reference_table);
   ~V8PerIsolateData();
 
-  typedef HashMap<const void*, v8::Eternal<v8::FunctionTemplate>>
-      V8FunctionTemplateMap;
+  using V8FunctionTemplateMap =
+      HashMap<const void*, v8::Eternal<v8::FunctionTemplate>>;
   V8FunctionTemplateMap& SelectInterfaceTemplateMap(const DOMWrapperWorld&);
   V8FunctionTemplateMap& SelectOperationTemplateMap(const DOMWrapperWorld&);
   bool HasInstance(const WrapperTypeInfo* untrusted,
                    v8::Local<v8::Value>,
                    V8FunctionTemplateMap&);
   v8::Local<v8::Object> FindInstanceInPrototypeChain(const WrapperTypeInfo*,
                                                      v8::Local<v8::Value>,
                                                      V8FunctionTemplateMap&);
 
+  // Members requried for snapshotted context, and should be instantiate
+  // before IsolateHolder.

[Yuki, 2017/05/30 14:35:58]

Members required for snapshotted contexts.
Need to be instantiated before |isolate_holder_| gets instantiated.

[peria, 2017/06/01 08:33:34]

Done.

+  std::unique_ptr<v8::SnapshotCreator> snapshot_creator_;
+  v8::StartupData startup_data_;
+
   gin::IsolateHolder isolate_holder_;
 
-  // m_interfaceTemplateMapFor{,Non}MainWorld holds function templates for
+  // interface_template_map_for_{,non_}main_world holds function templates for
   // the inerface objects.
   V8FunctionTemplateMap interface_template_map_for_main_world_;
   V8FunctionTemplateMap interface_template_map_for_non_main_world_;
+
+  // Members requried for snapshotted context.
+  using CopyablePersistent =

[Yuki, 2017/05/30 14:35:58]

I think that it's worth commenting that this is using v8::Persistent instead of
v8::Eternal and why we need to replace it.

[peria, 2017/06/01 08:33:34]

Acknowledged.

+      v8::Persistent<v8::FunctionTemplate,
+                     v8::CopyablePersistentTraits<v8::FunctionTemplate>>;
+  using V8FunctionTemplatePersistentMap =
+      HashMap<const void*, CopyablePersistent>;
+  V8FunctionTemplatePersistentMap interface_template_persistent_map_;

[Yuki, 2017/05/30 14:35:58]

interface_template_maps_for_snapshot_;
would be clearer?

[peria, 2017/06/01 08:33:34]

Done.

+  V8ContextMode v8_context_mode_;
+
   // m_operationTemplateMapFor{,Non}MainWorld holds function templates for
   // the cross-origin accessible DOM operations.
   V8FunctionTemplateMap operation_template_map_for_main_world_;
   V8FunctionTemplateMap operation_template_map_for_non_main_world_;
 
   // Contains lists of eternal names, such as dictionary keys.
   HashMap<const void*, Vector<v8::Eternal<v8::Name>>> eternal_name_cache_;
 
   std::unique_ptr<StringCache> string_cache_;
   std::unique_ptr<V8PrivateProperty> private_property_;
@@ skipping 11 matching lines @@
   Vector<std::unique_ptr<EndOfScopeTask>> end_of_scope_tasks_;
   std::unique_ptr<Data> thread_debugger_;
 
   Persistent<ActiveScriptWrappableSet> active_script_wrappables_;
   std::unique_ptr<ScriptWrappableVisitor> script_wrappable_visitor_;
 };
 
 }  // namespace blink
 
 #endif  // V8PerIsolateData_h