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

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

Index: third_party/WebKit/Source/bindings/core/v8/RemoteWindowProxy.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/RemoteWindowProxy.cpp b/third_party/WebKit/Source/bindings/core/v8/RemoteWindowProxy.cpp
index 74c90d25edaa45687aa49aa7c31fab60ad3dac3c..1c9060063465d69bc2487af7bad01b1020314442 100644
--- a/third_party/WebKit/Source/bindings/core/v8/RemoteWindowProxy.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/RemoteWindowProxy.cpp
@@ -66,6 +66,12 @@ void RemoteWindowProxy::DisposeContext(Lifecycle next_status) {
 #endif
   }
 
+  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;
 }