Move asserts for tracking global object detachment to WindowProxy.

third_party/WebKit/Source/bindings/core/v8/WindowProxy.h

Index: third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h b/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
index 393faea76c3a4d5293f46bec88833fe44eb5373a..945729d06065160b41a171c14896ef76dddfd739 100644
--- a/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
+++ b/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
@@ -168,9 +168,17 @@ class WindowProxy : public GarbageCollectedFinalized<WindowProxy> {
   Frame* frame() const { return m_frame.get(); }
   ScriptState* getScriptState() const { return m_scriptState.get(); }
 
+#if DCHECK_IS_ON()
+  void didAttachGlobalObject() { m_isGlobalObjectAttached = true; }
+  void didDetachGlobalObject() { m_isGlobalObjectAttached = false; }
+#endif
+
  private:
   v8::Isolate* const m_isolate;
   const Member<Frame> m_frame;
+#if DCHECK_IS_ON()
+  bool m_isGlobalObjectAttached = false;
+#endif
 
  protected:
   // TODO(dcheng): Move this to LocalWindowProxy once RemoteWindowProxy uses