Merge 101221 - Reland 101111 - Only deliver extension messages to contexts that care.

chrome/renderer/extensions/extension_helper.h

Index: chrome/renderer/extensions/extension_helper.h
===================================================================
--- chrome/renderer/extensions/extension_helper.h	(revision 103262)
+++ chrome/renderer/extensions/extension_helper.h	(working copy)
@@ -66,6 +66,8 @@
                                 const std::string& function_name,
                                 const base::ListValue& args,
                                 const GURL& event_url);
+  void OnExtensionDeliverMessage(int target_port_id,
+                                 const std::string& message);
   void OnExecuteCode(const ExtensionMsg_ExecuteCode_Params& params);
   void OnGetApplicationInfo(int page_id);
   void OnNotifyRendererViewType(ViewType::Type view_type);