Serve mojo WebUI resources from the same origin as the WebUI itself.

content/test/data/web_ui_mojo_shell_test.js

 // Copyright 2015 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 URL is defined in content/public/test/test_mojo_app.cc. It identifies
  * content_shell's out-of-process Mojo test app.
  */
 var TEST_APP_URL = 'system:content_mojo_test';
@@ skipping 17 matching lines @@
 
   return function() {
     domAutomationController.setAutomationId(0);
     var shellPipe = serviceRegistry.connectToService(shellMojom.Shell.name);
     var shell = new shellMojom.Shell.proxyClass(new router.Router(shellPipe));
     var urlRequest = new urlMojom.URLRequest({ url: TEST_APP_URL });
     shell.connectToApplication(urlRequest,
         function (services) {
           var test = connectToService(services, testMojom.TestMojoService);
           test.getRequestorURL().then(function(response) {
-            // The requestor URL seen by the app should be localhost because the
-            // connection comes from this script hosted on the test server.
-            domAutomationController.send(response.url == 'http://127.0.0.1/');
+            domAutomationController.send(
+                response.url == 'chrome://mojo-web-ui/');
           });
         },
         function (exposedServices) {});
   };
 });