Fix sizing issues in the tab modal signin flow.

chrome/browser/resources/sync_confirmation/sync_confirmation.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. */
 
 cr.define('sync.confirmation', function() {
   'use strict';
 
   function onConfirm(e) {
     chrome.send('confirm');
   }
 
   function onUndo(e) {
     chrome.send('undo');
   }
 
   function onGoToSettings(e) {
     chrome.send('goToSettings');
   }
 
   function initialize() {
     $('confirmButton').addEventListener('click', onConfirm);
     $('undoButton').addEventListener('click', onUndo);
     $('settingsLink').addEventListener('click', onGoToSettings);
     $('profile-picture').addEventListener('load', onPictureLoaded);
-    chrome.send('initialized');
+    chrome.send('initializedWithSize', [document.body.scrollHeight]);
   }
 
   function setUserImageURL(url) {
     $('profile-picture').src = url;
   }
 
   function onPictureLoaded(e) {
     $('picture-container').classList.add('loaded');
   }
 
   return {
     initialize: initialize,
     setUserImageURL: setUserImageURL
   };
 });
 
 document.addEventListener('DOMContentLoaded', sync.confirmation.initialize);