[Bindings] Create and use V8 context snapshots

third_party/WebKit/Source/web/WebKit.cpp

 /*
  * 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "public/web/WebKit.h"
 
 #include <memory>
 
 #include "bindings/core/v8/V8BindingForCore.h"
 #include "bindings/core/v8/V8GCController.h"
 #include "bindings/core/v8/V8Initializer.h"
+#include "bindings/core/v8/V8SnapshotCreator.h"
+#include "bindings/modules/v8/V8SnapshotExternalReferences.h"
 #include "core/animation/AnimationClock.h"
 #include "core/layout/LayoutTheme.h"
 #include "core/page/Page.h"
 #include "core/workers/WorkerBackingThread.h"
 #include "gin/public/v8_platform.h"
 #include "modules/ModulesInitializer.h"
 #include "platform/LayoutTestSupport.h"
 #include "platform/bindings/Microtask.h"
 #include "platform/heap/Heap.h"
 #include "platform/wtf/Assertions.h"
@@ skipping 26 matching lines @@
 
 static ModulesInitializer& GetModulesInitializer() {
   DEFINE_STATIC_LOCAL(std::unique_ptr<ModulesInitializer>, initializer,
                       (WTF::WrapUnique(new ModulesInitializer)));
   return *initializer;
 }
 
 void Initialize(Platform* platform) {
   Platform::Initialize(platform);
 
-  V8Initializer::InitializeMainThread();
+  // Refernce table must be updated before creating isolates.
+  V8SnapshotCreator::SetReferenceTable(

[Yuki, 2017/06/01 14:15:51]

Can we put this into InitializeMainThread() considering that V8Initializer
should be responsible all V8-related initialization?

[peria, 2017/06/20 10:20:14]

No, we can't.
V8Initializer is under core/, and V8SnapshotExternalReferences is under module/.
And what this line does must be a part of GetModulesInitializer().Initialize()
(2 lines below), but this work must be done before isolates' instantiation.

+      V8SnapshotExternalReferences::GetTable());
+  V8Initializer::InitializeMainThread(platform->TakeV8Snapshot());

[Yuki, 2017/06/01 14:15:51]

Can we simply pass |platform| and let InitliazeMainThread take care of the rest?

  V8Initializer::InitializeMainThread(platform);

looks simpler to me.

[peria, 2017/06/20 10:20:14]

Done.
I found we can call platform via Platform::Current(), so we don't need to pass
it here.

 
   GetModulesInitializer().Initialize();
 
   WebFactoryImpl::Initialize();
 
   // currentThread is null if we are running on a thread without a message loop.
   if (WebThread* current_thread = platform->CurrentThread()) {
     DCHECK(!g_end_of_task_runner);
     g_end_of_task_runner = new EndOfTaskRunner;
     current_thread->AddTaskObserver(g_end_of_task_runner);
@@ skipping 40 matching lines @@
 void MemoryPressureNotificationToWorkerThreadIsolates(
     v8::MemoryPressureLevel level) {
   WorkerBackingThread::MemoryPressureNotificationToWorkerThreadIsolates(level);
 }
 
 void SetRAILModeOnWorkerThreadIsolates(v8::RAILMode rail_mode) {
   WorkerBackingThread::SetRAILModeOnWorkerThreadIsolates(rail_mode);
 }
 
 }  // namespace blink