binding: Changes the association among global-proxy/global/window-instance.

third_party/WebKit/Source/bindings/core/v8/V8GCController.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 440 matching lines @@
 }
 
 void V8GCController::collectAllGarbageForTesting(v8::Isolate* isolate) {
   for (unsigned i = 0; i < 5; i++)
     isolate->RequestGarbageCollectionForTesting(
         v8::Isolate::kFullGarbageCollection);
 }
 
 class DOMWrapperTracer : public v8::PersistentHandleVisitor {
  public:
-  explicit DOMWrapperTracer(Visitor* visitor) : m_visitor(visitor) {}
+  explicit DOMWrapperTracer(Visitor* visitor) : m_visitor(visitor) {
+    DCHECK(m_visitor);
+  }
 
   void VisitPersistentHandle(v8::Persistent<v8::Value>* value,
                              uint16_t classId) override {
     if (classId != WrapperTypeInfo::NodeClassId &&
         classId != WrapperTypeInfo::ObjectClassId)
       return;
 
     const v8::Persistent<v8::Object>& wrapper =
         v8::Persistent<v8::Object>::Cast(*value);
 
-    if (m_visitor)
-      toWrapperTypeInfo(wrapper)->trace(m_visitor, toScriptWrappable(wrapper));
+    // |scriptWrappable| can be null if |wrapper| is a global proxy object,
+    // which points to nothing while a navigation.

[haraken, 2017/02/09 12:46:40]

Move this comment to toScriptWrappable.

[Yuki, 2017/02/10 07:47:21]

Done.

+    if (ScriptWrappable* scriptWrappable = toScriptWrappable(wrapper))
+      toWrapperTypeInfo(wrapper)->trace(m_visitor, scriptWrappable);
   }
 
  private:
   Visitor* m_visitor;
 };
 
 void V8GCController::traceDOMWrappers(v8::Isolate* isolate, Visitor* visitor) {
   DOMWrapperTracer tracer(visitor);
   isolate->VisitHandlesWithClassIds(&tracer);
 }
@@ skipping 53 matching lines @@
   double startTime = WTF::currentTimeMS();
   v8::HandleScope scope(isolate);
   PendingActivityVisitor visitor(isolate, executionContext);
   toIsolate(executionContext)->VisitHandlesWithClassIds(&visitor);
   scanPendingActivityHistogram.count(
       static_cast<int>(WTF::currentTimeMS() - startTime));
   return visitor.pendingActivityFound();
 }
 
 }  // namespace blink