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

Source/core/frame/DOMWindow.h

Index: Source/core/frame/DOMWindow.h
diff --git a/Source/core/frame/DOMWindow.h b/Source/core/frame/DOMWindow.h
new file mode 100644
index 0000000000000000000000000000000000000000..15dbaf78dddf183e8aeda26807e112ea68684aa2
--- /dev/null
+++ b/Source/core/frame/DOMWindow.h
@@ -0,0 +1,14 @@
+// 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.
+
+namespace blink {
+
+class ScriptWrappable;
+
+class DOMWindow {

[haraken, 2014/10/22 00:59:14]

I'm curious why DOMWindow can't inherit from ScriptWrappableBase?

[dcheng, 2014/10/22 01:01:46]

LocalDOMWindow is an EventTarget (and I don't think it makes sense for
RemoteDOMWindow to be an EventTarget -- I don't think you can register an event
listener on a cross-origin DOMWindow). If this was also a ScriptWrappable, then
you would have to explicitly say you wanted to use the ScriptWrappableBase from
EventTargetWithInlineData or the ScriptWrappableBase from DOMWindow.

+public:
+    virtual ScriptWrappable* toScriptWrappable() = 0;
+};
+
+} // namespace blink