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

Source/core/frame/RemoteFrame.cpp

Index: Source/core/frame/RemoteFrame.cpp
diff --git a/Source/core/frame/RemoteFrame.cpp b/Source/core/frame/RemoteFrame.cpp
index 1ab261e0d7b03adc76d9ec25ab292fe3c9a72243..1b0e04e5b191d34055b23181db1a5b72f3ec9ea7 100644
--- a/Source/core/frame/RemoteFrame.cpp
+++ b/Source/core/frame/RemoteFrame.cpp
@@ -27,6 +27,12 @@ RemoteFrame::~RemoteFrame()
     setView(nullptr);
 }
 
+void RemoteFrame::trace(Visitor* visitor)
+{
+    visitor->trace(m_view);
+    Frame::trace(visitor);
+}
+
 void RemoteFrame::navigate(Document& originDocument, const KURL& url, bool lockBackForwardList)
 {
     // The process where this frame actually lives won't have sufficient information to determine
@@ -49,12 +55,6 @@ void RemoteFrame::forwardInputEvent(Event* event)
     remoteFrameClient()->forwardInputEvent(event);
 }
 
-void RemoteFrame::trace(Visitor* visitor)
-{
-    visitor->trace(m_view);
-    Frame::trace(visitor);
-}
-
 void RemoteFrame::setView(PassRefPtrWillBeRawPtr<RemoteFrameView> view)
 {
     // Oilpan: as RemoteFrameView performs no finalization actions,