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

Source/core/loader/EmptyClients.h

 /*
  * Copyright (C) 2006 Eric Seidel (eric@webkit.org)
  * Copyright (C) 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 145 matching lines @@
 };
 
 class CORE_EXPORT EmptyFrameLoaderClient : public FrameLoaderClient {
     WTF_MAKE_NONCOPYABLE(EmptyFrameLoaderClient); WTF_MAKE_FAST_ALLOCATED(EmptyFrameLoaderClient);
 public:
     EmptyFrameLoaderClient() { }
     virtual ~EmptyFrameLoaderClient() {  }
 
     virtual bool hasWebView() const override { return true; } // mainly for assertions
 
+    virtual bool inShadowTree() const override { return false; }
+
     virtual Frame* opener() const override { return 0; }
     virtual void setOpener(Frame*) override { }
 
     virtual Frame* parent() const override { return 0; }
     virtual Frame* top() const override { return 0; }
     virtual Frame* previousSibling() const override { return 0; }
     virtual Frame* nextSibling() const override { return 0; }
     virtual Frame* firstChild() const override { return 0; }
     virtual Frame* lastChild() const override { return 0; }
     virtual void willBeDetached() override { }
@@ skipping 131 matching lines @@
     virtual ~EmptyDragClient() {}
     virtual DragDestinationAction actionMaskForDrag(DragData*) override { return DragDestinationActionNone; }
     virtual void startDrag(DragImage*, const IntPoint&, const IntPoint&, DataTransfer*, LocalFrame*, bool) override { }
 };
 
 CORE_EXPORT void fillWithEmptyClients(Page::PageClients&);
 
 } // namespace blink
 
 #endif // EmptyClients_h