[DevTools] Use WebLayerTreeView::layerTreeId() for instrumentation.

Source/web/WebFrameWidgetImpl.h

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 122 matching lines @@
     void sendResizeEventAndRepaint();
 
     void updateMainFrameLayoutSize();
 
     void setIgnoreInputEvents(bool newValue);
 
     // Returns the page object associated with this widget. This may be null when
     // the page is shutting down, but will be valid at all other times.
     Page* page() const { return m_page; }
 
+    WebLayerTreeView* layerTreeView() const { return m_layerTreeView; }
+
     // Returns true if the event leads to scrolling.
     static bool mapKeyCodeForScroll(
         int keyCode,
         ScrollDirection*,
         ScrollGranularity*);
 
 private:
     friend class WebFrameWidget; // For WebFrameWidget::create.
     friend class WTF::RefCounted<WebFrameWidgetImpl>;
 
@@ skipping 50 matching lines @@
     bool m_suppressNextKeypressEvent;
 
     bool m_ignoreInputEvents;
 
     static const WebInputEvent* m_currentInputEvent;
 };
 
 } // namespace blink
 
 #endif