Improve window.closed fidelity.

Source/core/frame/DOMWindow.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DOMWindow_h
 #define DOMWindow_h
 
 #include "core/CoreExport.h"
 #include "core/events/EventTarget.h"
 #include "core/frame/DOMWindowBase64.h"
@@ skipping 196 matching lines @@
     DEFINE_MAPPED_ATTRIBUTE_EVENT_LISTENER(webkitanimationiteration, webkitAnimationIteration);
     DEFINE_MAPPED_ATTRIBUTE_EVENT_LISTENER(webkitanimationend, webkitAnimationEnd);
     DEFINE_MAPPED_ATTRIBUTE_EVENT_LISTENER(webkittransitionend, webkitTransitionEnd);
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(orientationchange);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(touchstart);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(touchmove);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(touchend);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(touchcancel);
 
+protected:
+    DOMWindow();
+
+    // Set to true when close() has been called. Needed for
+    // |window.closed| determinism; having it return 'true'
+    // only after the render widget's deferred window close
+    // operation has been performed, exposes (confusing)
+    // implementation details to scripts.
+    bool m_windowIsClosing;
+
 private:
     mutable RefPtrWillBeMember<Location> m_location;
 };
 
 } // namespace blink
 
 #endif // DOMWindow_h