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

third_party/WebKit/Source/core/frame/FrameOwner.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 FrameOwner_h
 #define FrameOwner_h
 
 #include "core/CoreExport.h"
 #include "core/dom/SandboxFlags.h"
 #include "platform/heap/Handle.h"
@@ skipping 34 matching lines @@
     USING_GARBAGE_COLLECTED_MIXIN(DummyFrameOwner);
 public:
     static DummyFrameOwner* create()
     {
         return new DummyFrameOwner;
     }
 
     DEFINE_INLINE_VIRTUAL_TRACE() { FrameOwner::trace(visitor); }
 
     // FrameOwner overrides:
-    bool isLocal() const override { return false; }
-    bool isRemote() const override { return false; }
     void setContentFrame(Frame&) override { }
     void clearContentFrame() override { }
     SandboxFlags getSandboxFlags() const override { return SandboxNone; }
     void dispatchLoad() override { }
     void renderFallbackContent() override { }
     ScrollbarMode scrollingMode() const override { return ScrollbarAuto; }
     int marginWidth() const override { return -1; }
     int marginHeight() const override { return -1; }
     bool allowFullscreen() const override { return false; }
+
+private:
+    // Intentionally private to prevent redundant checks when the type is
+    // already DummyFrameOwner.
+    bool isLocal() const override { return false; }
+    bool isRemote() const override { return false; }
 };
 
 } // namespace blink
 
 #endif // FrameOwner_h