Move extension messages to their own file and add a RenderViewObserver to start moving the extens...

content/browser/tab_contents/tab_contents.h

Index: content/browser/tab_contents/tab_contents.h
===================================================================
--- content/browser/tab_contents/tab_contents.h	(revision 79468)
+++ content/browser/tab_contents/tab_contents.h	(working copy)
@@ -79,9 +79,9 @@
 class TabContentsSSLHelper;
 class TabContentsView;
 class URLPattern;
+struct ExtensionHostMsg_DomMessage_Params;
 struct RendererPreferences;
 struct ThumbnailScore;
-struct ViewHostMsg_DomMessage_Params;
 struct ViewHostMsg_FrameNavigate_Params;
 struct WebPreferences;
 
@@ -911,7 +911,8 @@
                               WindowOpenDisposition disposition);
   virtual void DomOperationResponse(const std::string& json_string,
                                     int automation_id);
-  virtual void ProcessWebUIMessage(const ViewHostMsg_DomMessage_Params& params);
+  virtual void ProcessWebUIMessage(
+      const ExtensionHostMsg_DomMessage_Params& params);
   virtual void ProcessExternalHostMessage(const std::string& message,
                                           const std::string& origin,
                                           const std::string& target);