Make sure ports are closed when they're no longer used.

chrome/renderer/resources/extensions/miscellaneous_bindings.js

 // Copyright (c) 2012 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.
 
 // This script contains unprivileged javascript APIs related to chrome
 // extensions.  It is loaded by any extension-related context, such as content
 // scripts or background pages.
 // See user_script_slave.cc for script that is loaded by content scripts only.
 
 var chrome = chrome || {};
 (function () {
   native function CloseChannel(portId, notifyBrowser);
   native function PortAddRef(portId);
   native function PortRelease(portId);
   native function PostMessage(portId, msg);
   native function GetChromeHidden();
   native function Print();
+  native function BindToGC();
 
   var chromeHidden = GetChromeHidden();
   var manifestVersion;
   var extensionId;
 
   // The reserved channel name for the sendRequest API.
   chromeHidden.kRequestChannel = "chrome.extension.sendRequest";
 
   // Map of port IDs to port object.
   var ports = {};
@@ skipping 88 matching lines @@
       tab = chromeHidden.JSON.parse(tab);
     var sender = {tab: tab, id: sourceExtensionId};
 
     // Special case for sendRequest/onRequest.
     if (channelName == chromeHidden.kRequestChannel) {
       var requestEvent = (isExternal ?
           chrome.extension.onRequestExternal : chrome.extension.onRequest);
       if (requestEvent.hasListeners()) {
         var port = chromeHidden.Port.createPort(portId, channelName);
         port.onMessage.addListener(function(request) {
-          requestEvent.dispatch(request, sender, function(response) {
+          var responseCallback = function(response) {
             if (port) {
               port.postMessage(response);
               port = null;
             } else {
               // We nulled out port when sending the response, and now the page
               // is trying to send another response for the same request.
               var errorMsg =
                   "Cannot send a response more than once per " +
                   "chrome.extension.onRequest listener per document (message " +
                   "was sent by extension " + sourceExtensionId;
               if (sourceExtensionId != targetExtensionId) {
                 errorMsg += " for extension " + targetExtensionId;
               }
               errorMsg += ").";
               chrome.extension.lastError = {"message": errorMsg};
               console.error("Could not send response: " + errorMsg);
             }
+          };
+          // In case the extension never invokes the responseCallback, and also
+          // doesn't keep a reference to it, we need to clean up the port. Do
+          // so by attaching to the garbage collection of the responseCallback
+          // using some native hackery.
+          BindToGC(responseCallback, function() {
+            if (port) {
+              port.postMessage(null);

[Matt Perry, 2012/03/13 19:54:39]

Change this to port.disconnect(); We shouldn't send a response on the
extension's behalf. See http://crbug.com/93566 for more info.

BTW, please add that bug to the CL description, since this change will fix it.

+              port = null;
+            }
           });
+          requestEvent.dispatch(request, sender, responseCallback);
         });
       }
       return;
     }
 
     var connectEvent = (isExternal ?
         chrome.extension.onConnectExternal : chrome.extension.onConnect);
     if (connectEvent.hasListeners()) {
       var port = chromeHidden.Port.createPort(portId, channelName);
       port.sender = sender;
@@ skipping 49 matching lines @@
     chrome.extension = chrome.extension || {};
 
     if (manifestVersion < 2) {
       chrome.self = chrome.extension;
       chrome.extension.inIncognitoTab = inIncognitoContext;
     }
 
     chrome.extension.inIncognitoContext = inIncognitoContext;
   });
 })();