Plumb whether or not a frame is in shadow DOM to the embedder.

Source/core/frame/FrameClient.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 FrameClient_h
 #define FrameClient_h
 
 #include "core/CoreExport.h"
 
 namespace blink {
 
 class Frame;
 class LocalFrame;
 class MessageEvent;
 class SecurityOrigin;
 
 class CORE_EXPORT FrameClient {
 public:
+    virtual bool inShadowTree() const = 0;
+
+    // TODO(dcheng): Move this into FrameLoaderClient, since remote frames don't
+    // need this.
     virtual void willBeDetached() = 0;
     virtual void detached() = 0;
 
     virtual Frame* opener() const = 0;
     virtual void setOpener(Frame*) = 0;
 
     virtual Frame* parent() const = 0;
     virtual Frame* top() const = 0;
     virtual Frame* previousSibling() const = 0;
     virtual Frame* nextSibling() const = 0;
     virtual Frame* firstChild() const = 0;
     virtual Frame* lastChild() const = 0;
 
     // Returns true if the embedder intercepted the postMessage call
     virtual bool willCheckAndDispatchMessageEvent(SecurityOrigin* /*target*/, MessageEvent*, LocalFrame* /*sourceFrame*/) const { return false; }
 
     virtual ~FrameClient() { }
 };
 
 } // namespace blink
 
 #endif // FrameClient_h