Clean up forward declarations in Source/core/inspector

Source/core/inspector/InspectorResourceAgent.h

Index: Source/core/inspector/InspectorResourceAgent.h
diff --git a/Source/core/inspector/InspectorResourceAgent.h b/Source/core/inspector/InspectorResourceAgent.h
index c0d114d98cabe4241f11367a019d07f9ec09b088..09c8c0e8cee9577706a89931835f2084227139c4 100644
--- a/Source/core/inspector/InspectorResourceAgent.h
+++ b/Source/core/inspector/InspectorResourceAgent.h
@@ -39,10 +39,6 @@
 #include "wtf/PassOwnPtr.h"
 #include "wtf/text/WTFString.h"
 
-namespace WTF {
-class String;
-}
-
 namespace blink {
 
 class Resource;
@@ -54,11 +50,9 @@ class LocalFrame;
 class HTTPHeaderMap;
 class InspectorFrontend;
 class InspectorPageAgent;
-class InstrumentingAgents;
 class JSONObject;
 class KURL;
 class NetworkResourcesData;
-class Page;
 class ResourceError;
 class ResourceLoader;
 class ResourceRequest;