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

third_party/WebKit/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 "bindings/core/v8/Transferables.h"
 #include "core/CoreExport.h"
 #include "core/events/EventTarget.h"
@@ skipping 32 matching lines @@
 class StyleMedia;
 
 class CORE_EXPORT DOMWindow : public EventTargetWithInlineData, public DOMWindowBase64 {
     DEFINE_WRAPPERTYPEINFO();
 public:
     ~DOMWindow() override;
 
     // GarbageCollectedFinalized overrides:
     DECLARE_VIRTUAL_TRACE();
 
-    virtual bool isLocalDOMWindow() const { return false; }
-    virtual bool isRemoteDOMWindow() const { return false; }
+    virtual bool isLocalDOMWindow() const = 0;
+    virtual bool isRemoteDOMWindow() const = 0;
 
     virtual Frame* frame() const = 0;
 
     // ScriptWrappable overrides:
     v8::Local<v8::Object> wrap(v8::Isolate*, v8::Local<v8::Object> creationContext) final;
     v8::Local<v8::Object> associateWithWrapper(v8::Isolate*, const WrapperTypeInfo*, v8::Local<v8::Object> wrapper) final;
 
     // EventTarget overrides:
     const AtomicString& interfaceName() const override;
     const DOMWindow* toDOMWindow() const override;
@@ skipping 162 matching lines @@
     // implementation details to scripts.
     bool m_windowIsClosing;
 
 private:
     mutable Member<Location> m_location;
 };
 
 } // namespace blink
 
 #endif // DOMWindow_h