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

chrome/renderer/resources/renderer_extension_bindings.js

Index: chrome/renderer/resources/renderer_extension_bindings.js
===================================================================
--- chrome/renderer/resources/renderer_extension_bindings.js	(revision 103262)
+++ chrome/renderer/resources/renderer_extension_bindings.js	(working copy)
@@ -46,6 +46,13 @@
 
   chromeHidden.Port = {};
 
+  // Returns true if the specified port id is in this context. This is used by
+  // the C++ to avoid creating the javascript message for all the contexts that
+  // don't care about a particular message.
+  chromeHidden.Port.hasPort = function(portId) {
+    return portId in ports;
+  };
+
   // Hidden port creation function.  We don't want to expose an API that lets
   // people add arbitrary port IDs to the port list.
   chromeHidden.Port.createPort = function(portId, opt_name) {