Clean up forward declarations in Source/core/inspector

Source/core/inspector/InspectorMemoryAgent.h

 /*
  * Copyright (C) 2011 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 19 matching lines @@
 
 #ifndef InspectorMemoryAgent_h
 #define InspectorMemoryAgent_h
 
 #include "core/InspectorFrontend.h"
 #include "core/inspector/InspectorBaseAgent.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
-class InstrumentingAgents;
-
 typedef String ErrorString;
 
 class InspectorMemoryAgent final : public InspectorBaseAgent<InspectorMemoryAgent>, public InspectorBackendDispatcher::MemoryCommandHandler {
     WTF_MAKE_NONCOPYABLE(InspectorMemoryAgent);
 public:
     static PassOwnPtrWillBeRawPtr<InspectorMemoryAgent> create()
     {
         return adoptPtrWillBeNoop(new InspectorMemoryAgent());
     }
     virtual ~InspectorMemoryAgent();
 
     virtual void getDOMCounters(ErrorString*, int* documents, int* nodes, int* jsEventListeners) override;
 
     virtual void setFrontend(InspectorFrontend*) override;
     virtual void clearFrontend() override;
 
 private:
     InspectorMemoryAgent();
 
     InspectorFrontend::Memory* m_frontend;
 };
 
 } // namespace blink
 
 #endif // !defined(InspectorMemoryAgent_h)