Disallow local/remote checks on subclasses of Frame, FrameOwner and DOMWindow.

third_party/WebKit/Source/core/frame/RemoteDOMWindow.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 RemoteDOMWindow_h
 #define RemoteDOMWindow_h
 
 #include "core/frame/DOMWindow.h"
 #include "core/frame/RemoteFrame.h"
 
 namespace blink {
 
 class RemoteDOMWindow final : public DOMWindow {
 public:
     static RemoteDOMWindow* create(RemoteFrame& frame)
     {
         return new RemoteDOMWindow(frame);
     }
 
     // EventTarget overrides:
     ExecutionContext* getExecutionContext() const override;
 
     // DOMWindow overrides:
     DECLARE_VIRTUAL_TRACE();
-    bool isRemoteDOMWindow() const override { return true; }
     RemoteFrame* frame() const override;
     Screen* screen() const override;
     History* history() const override;
     BarProp* locationbar() const override;
     BarProp* menubar() const override;
     BarProp* personalbar() const override;
     BarProp* scrollbars() const override;
     BarProp* statusbar() const override;
     BarProp* toolbar() const override;
     Navigator* navigator() const override;
@@ skipping 45 matching lines @@
 
     void frameDetached();
 
 protected:
     // Protected DOMWindow overrides:
     void schedulePostMessage(MessageEvent*, PassRefPtr<SecurityOrigin> target, Document* source) override;
 
 private:
     explicit RemoteDOMWindow(RemoteFrame&);
 
+    // Intentionally private to prevent redundant checks when the type is
+    // already RemoteDOMWindow.
+    bool isLocalDOMWindow() const override { return false; }
+    bool isRemoteDOMWindow() const override { return true; }
+
     Member<RemoteFrame> m_frame;
 };
 
 } // namespace blink
 
 #endif // DOMWindow_h