Add a basic DOMWindow base class and use it in WindowProxy.

Source/core/frame/LocalFrame.h

Index: Source/core/frame/LocalFrame.h
diff --git a/Source/core/frame/LocalFrame.h b/Source/core/frame/LocalFrame.h
index 5a2e45062f47c1dbee0526a68a16caec7596eeb5..419ad462e4f2a36ccbfe49bf964e6d9e18d4e00e 100644
--- a/Source/core/frame/LocalFrame.h
+++ b/Source/core/frame/LocalFrame.h
@@ -79,6 +79,7 @@ namespace blink {
         virtual ~LocalFrame();
         virtual void trace(Visitor*) override;
         virtual bool isLocalFrame() const override { return true; }
+        virtual LocalDOMWindow* domWindow() const override;
         virtual void navigate(Document& originDocument, const KURL&, bool lockBackForwardList) override;
         virtual void detach() override;
         virtual void disconnectOwnerElement() override;
@@ -88,7 +89,7 @@ namespace blink {
 
         void willDetachFrameHost();
 
-        virtual void setDOMWindow(PassRefPtrWillBeRawPtr<LocalDOMWindow>) override;
+        void setDOMWindow(PassRefPtrWillBeRawPtr<LocalDOMWindow>);
         FrameView* view() const;
         Document* document() const;
         void setPagePopupOwner(Element&);
@@ -176,6 +177,7 @@ namespace blink {
         mutable NavigationScheduler m_navigationScheduler;
 
         RefPtrWillBeMember<FrameView> m_view;
+        RefPtrWillBeMember<LocalDOMWindow> m_domWindow;
         // Usually 0. Non-null if this is the top frame of PagePopup.
         RefPtrWillBeMember<Element> m_pagePopupOwner;