[Bindings] Create and use V8 context snapshots

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

Index: third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
diff --git a/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h b/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
index dbb2c0e48ce297657a6a427b3789bb7ba8675364..70efb61c1374c5b630bfbd40d309e5b3e8de3544 100644
--- a/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
+++ b/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
@@ -59,6 +59,12 @@ class PLATFORM_EXPORT V8PerIsolateData {
   WTF_MAKE_NONCOPYABLE(V8PerIsolateData);
 
  public:
+  enum class V8ContextMode {
+    kTakeSnapshot,
+    kDontUseSnapshot,
+    kUseSnapshot,
+  };
+
   class EndOfScopeTask {
     USING_FAST_MALLOC(EndOfScopeTask);
 
@@ -100,7 +106,9 @@ class PLATFORM_EXPORT V8PerIsolateData {
     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);
@@ -117,6 +125,7 @@ class PLATFORM_EXPORT V8PerIsolateData {
                               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(); }
 
@@ -140,6 +149,8 @@ class PLATFORM_EXPORT V8PerIsolateData {
   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.
@@ -221,11 +232,13 @@ class PLATFORM_EXPORT V8PerIsolateData {
   }
 
  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,
@@ -235,12 +248,27 @@ class PLATFORM_EXPORT V8PerIsolateData {
                                                      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_;