v8binding: Makes WindowProxy::global_proxy_ a weak reference when detached.

third_party/WebKit/Source/bindings/core/v8/LocalWindowProxy.cpp

 /*
  * Copyright (C) 2008, 2009, 2011 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 88 matching lines @@
   }
 
   script_state_->DisposePerContextData();
 
   // It's likely that disposing the context has created a lot of
   // garbage. Notify V8 about this so it'll have a chance of cleaning
   // it up when idle.
   V8GCForContextDispose::Instance().NotifyContextDisposed(
       GetFrame()->IsMainFrame());
 
+  if (next_status == Lifecycle::kFrameIsDetached) {
+    // The context's frame is detached from the DOM, so there shouldn't be a
+    // strong reference to the context.
+    global_proxy_.SetPhantom();
+  }
+
   DCHECK_EQ(lifecycle_, Lifecycle::kContextIsInitialized);
   lifecycle_ = next_status;
 }
 
 void LocalWindowProxy::Initialize() {
   TRACE_EVENT1("v8", "LocalWindowProxy::initialize", "isMainWindow",
                GetFrame()->IsMainFrame());
   SCOPED_BLINK_UMA_HISTOGRAM_TIMER(
       GetFrame()->IsMainFrame()
           ? "Blink.Binding.InitializeMainLocalWindowProxy"
@@ skipping 324 matching lines @@
 
   SetSecurityToken(origin);
 }
 
 LocalWindowProxy::LocalWindowProxy(v8::Isolate* isolate,
                                    LocalFrame& frame,
                                    RefPtr<DOMWrapperWorld> world)
     : WindowProxy(isolate, frame, std::move(world)) {}
 
 }  // namespace blink