Support for auth code based authentication flow for both app and web UI driven flow.

chrome/browser/resources/gaia_auth/main.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.
 
 function Authenticator() {
 }
 
 Authenticator.getInstance = function() {
   if (!Authenticator.instance_) {
     Authenticator.instance_ = new Authenticator();
@@ skipping 92 matching lines @@
       if (this.attemptToken_ == msg.attemptToken) {
         var msg = {
           'method': 'completeLogin',
           'email': this.email_,
           'password': this.password_
         };
         window.parent.postMessage(msg, this.PARENT_PAGE);
       } else {
         console.log('#### Authenticator.onMessage: unexpected attemptToken!?');
       }
+    } else if (msg.method == 'confirmAuthentication' &&
+               this.isInternalMessage_(e)) {
+      var msg = {
+        'method': 'completeAuthentication',
+        'email': msg.email,
+        'authCode': msg.authCode
+      };
+      window.parent.postMessage(msg, this.PARENT_PAGE);
     } else {
       console.log('#### Authenticator.onMessage: unknown message + origin!?');
     }
   }
 };
 
 Authenticator.getInstance().initialize();