Add fallback mechanism to release Extension ports if the JS context has been destroyed.

extensions/renderer/resources/messaging.js

 // Copyright 2014 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.
 
 // chrome.runtime.messaging API implementation.
 
   // TODO(kalman): factor requiring chrome out of here.
   var chrome = requireNative('chrome').GetChrome();
   var lastError = require('lastError');
   var logActivity = requireNative('activityLogger');
@@ skipping 110 matching lines @@
           // We nulled out port when sending the response, and now the page
           // is trying to send another response for the same request.
           handleSendRequestError(isSendMessage, responseCallbackPreserved,
                                  sourceExtensionId, targetExtensionId);
         }
       };
       // 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.
+      //
+      // If the context is destroyed before this has a chance to execute,
+      // BindToGC knows to release |portId| (important for updating C++ state
+      // both in this renderer and on the other end). We don't need to clear
+      // any JavaScript state, as calling destroy_() would usually do - but
+      // the context has been destroyed, so there isn't any JS state to clear.
       messagingNatives.BindToGC(responseCallback, function() {
         if (port) {
           privates(port).impl.destroy_();
           port = null;
         }
-      });
+      }, portId);
       var rv = requestEvent.dispatch(request, sender, responseCallback);
       if (isSendMessage) {
         responseCallbackPreserved =
             rv && rv.results && $Array.indexOf(rv.results, true) > -1;
         if (!responseCallbackPreserved && port) {
           // If they didn't access the response callback, they're not
           // going to send a response, so clean up the port immediately.
           privates(port).impl.destroy_();
           port = null;
         }
@@ skipping 182 matching lines @@
 exports.kNativeMessageChannel = kNativeMessageChannel;
 exports.createPort = createPort;
 exports.sendMessageImpl = sendMessageImpl;
 exports.sendMessageUpdateArguments = sendMessageUpdateArguments;
 
 // For C++ code to call.
 exports.hasPort = hasPort;
 exports.dispatchOnConnect = dispatchOnConnect;
 exports.dispatchOnDisconnect = dispatchOnDisconnect;
 exports.dispatchOnMessage = dispatchOnMessage;