Use webview.request in OAuth scope approval dialog.

chrome/browser/resources/identity_scope_approval_dialog/scope_approval_dialog.js

 // Copyright 2013 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.
 
 var webview;
 
 /**
  * Points the webview to the starting URL of a scope authorization
  * flow, and unhides the dialog once the page has loaded.
  * @param {string} url The url of the authorization entry point.
  * @param {Object} win The dialog window that contains this page. Can
  *     be left undefined if the caller does not want to display the
  *     window.
  */
 function loadAuthUrlAndShowWindow(url, win) {
   // Send popups from the webview to a normal browser window.
   webview.addEventListener('newwindow', function(e) {
     e.window.discard();
     window.open(e.targetUrl);
   });
 
   // Request a customized view from GAIA.
-  webview.onBeforeSendHeaders.addListener(function(details) {
+  webview.request.onBeforeSendHeaders.addListener(function(details) {
     headers = details.requestHeaders || [];
     headers.push({'name': 'X-Browser-View',
                   'value': 'embedded'});
     return { requestHeaders: headers };
   }, {
     urls: ['https://accounts.google.com/*'],
   }, ['blocking', 'requestHeaders']);
 
   if (url.toLowerCase().indexOf('https://accounts.google.com/') != 0)
     document.querySelector('.titlebar').classList.add('titlebar-border');
@@ skipping 22 matching lines @@
     }
 
     insertRule('.titlebar-close-button', resources.IDR_CLOSE_DIALOG);
     insertRule('.titlebar-close-button:hover', resources.IDR_CLOSE_DIALOG_H);
     insertRule('.titlebar-close-button:active', resources.IDR_CLOSE_DIALOG_P);
 
     document.title = resources.IDS_EXTENSION_PERMISSIONS_PROMPT_TITLE;
   });
 });