Fix some issues with extension messaging:

chrome/renderer/resources/renderer_extension_bindings.js

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // -----------------------------------------------------------------------------
 // NOTE: If you change this file you need to touch renderer_resources.grd to
 // have your change take effect.
 // -----------------------------------------------------------------------------
 
 var chrome = chrome || {};
@@ skipping 11 matching lines @@
   // Port object.  Represents a connection to another script context through
   // which messages can be passed.
   chrome.Port = function(portId) {
     if (ports[portId]) {
       throw new Error("Port '" + portId + "' already exists.");
     }
     this.portId_ = portId;  // TODO(mpcomplete): readonly
     this.onDisconnect = new chrome.Event();
     this.onMessage = new chrome.Event();
     ports[portId] = this;
-    
+
+    var port = this;
     chromeHidden.onUnload.addListener(function() {
-      this.disconnect();
+      port.disconnect();
     });
   };
 
   chromeHidden.Port = {};
 
   // Called by native code when a channel has been opened to this context.
-  chromeHidden.Port.dispatchOnConnect = function(portId, tab) {
-    var port = new chrome.Port(portId);
-    if (tab) {
-      tab = JSON.parse(tab);
+  chromeHidden.Port.dispatchOnConnect = function(portId, tab, extensionId) {
+    // Only create a new Port if someone is actually listening for a connection.
+    // In addition to being an optimization, this also fixes a bug where if 2
+    // channels were opened to and from the same process, closing one would
+    // close both.
+    var connectEvent = "channel-connect:" + (extensionId || "");
+    if (chromeHidden.Event.hasListener(connectEvent)) {
+      var port = new chrome.Port(portId);
+      if (tab) {
+        tab = JSON.parse(tab);
+      }
+      port.tab = tab;
+      chromeHidden.Event.dispatch(connectEvent, [port]);
     }
-    port.tab = tab;
-    chromeHidden.Event.dispatch("channel-connect", [port]);
   };
 
   // Called by native code when a channel has been closed.
   chromeHidden.Port.dispatchOnDisconnect = function(portId) {
     var port = ports[portId];
     if (port) {
       port.onDisconnect.dispatch(port);
       delete ports[portId];
     }
   };
@@ skipping 37 matching lines @@
       throw new Error("No such extension: '" + this.id_ + "'");
     return new chrome.Port(portId);
   };
 
   // Returns a resource URL that can be used to fetch a resource from this
   // extension.
   chrome.Extension.prototype.getURL = function(path) {
     return "chrome-extension://" + this.id_ + "/" + path;
   };
 })();