Revert of DevTools: use per-LocalFrame instrumenting agents instead of per-Page ones.

Source/core/frame/LocalFrame.h

Index: Source/core/frame/LocalFrame.h
diff --git a/Source/core/frame/LocalFrame.h b/Source/core/frame/LocalFrame.h
index c9e2193a7600891d7f30a5f22753319478e0a6e1..e68a17fd2a3da52db93a5f4aa7524b25622881fc 100644
--- a/Source/core/frame/LocalFrame.h
+++ b/Source/core/frame/LocalFrame.h
@@ -57,7 +57,6 @@
     class InputMethodController;
     class IntPoint;
     class IntSize;
-    class InstrumentingAgents;
     class LocalDOMWindow;
     class Node;
     class Range;
@@ -125,9 +124,6 @@
         // FIXME: This is a temporary hack to support RemoteFrames, and callers
         // should be updated to avoid storing things on the main frame.
         LocalFrame* localFrameRoot();
-
-        InstrumentingAgents* instrumentingAgents();
-        void setInstrumentingAgents(InstrumentingAgents*);
 
     // ======== All public functions below this point are candidates to move out of LocalFrame into another class. ========
 
@@ -226,8 +222,6 @@
         float m_textZoomFactor;
 
         bool m_inViewSourceMode;
-
-        RefPtrWillBeMember<InstrumentingAgents> m_instrumentingAgents;
     };
 
     inline void LocalFrame::init()