Clean up forward declarations in Source/core/inspector

Source/core/inspector/InspectorDOMAgent.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 39 matching lines @@
 class CharacterData;
 class DOMEditor;
 class Document;
 class Element;
 class EventTarget;
 class ExceptionState;
 class InspectorFrontend;
 class InspectorHistory;
 class InspectorOverlay;
 class InspectorPageAgent;
-class InspectorState;
-class InstrumentingAgents;
 class Node;
 class PlatformGestureEvent;
 class PlatformTouchEvent;
 class RevalidateStyleAttributeTask;
 class ShadowRoot;
 
 struct HighlightConfig;
 
 typedef String ErrorString;
 
@@ skipping 204 matching lines @@
     OwnPtrWillBeMember<InspectorHistory> m_history;
     OwnPtrWillBeMember<DOMEditor> m_domEditor;
     bool m_suppressAttributeModifiedEvent;
     RawPtrWillBeMember<Listener> m_listener;
 };
 
 
 } // namespace blink
 
 #endif // !defined(InspectorDOMAgent_h)