Clean up forward declarations in Source/core/inspector

Source/core/inspector/InspectorLayerTreeAgent.h

 /*
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 25 matching lines @@
 #include "core/inspector/InspectorBaseAgent.h"
 #include "core/rendering/RenderLayer.h"
 #include "platform/Timer.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class GraphicsContextSnapshot;
-class InstrumentingAgents;
 class Page;
 class RenderLayerCompositor;
 
 typedef String ErrorString;
 
 class InspectorLayerTreeAgent final : public InspectorBaseAgent<InspectorLayerTreeAgent>, public InspectorBackendDispatcher::LayerTreeCommandHandler {
 public:
     static PassOwnPtrWillBeRawPtr<InspectorLayerTreeAgent> create(Page* page)
     {
         return adoptPtrWillBeNoop(new InspectorLayerTreeAgent(page));
@@ skipping 46 matching lines @@
     Vector<int, 2> m_pageOverlayLayerIds;
 
     typedef HashMap<String, RefPtr<GraphicsContextSnapshot> > SnapshotById;
     SnapshotById m_snapshotById;
 };
 
 } // namespace blink
 
 
 #endif // !defined(InspectorLayerTreeAgent_h)