Fix layout of the sync and sign-in error dialogs when the page zoom is increased.

chrome/browser/resources/signin/signin_error/signin_error.js

 /* Copyright 2016 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('signin.error', function() {
   'use strict';
 
   function initialize() {
     document.addEventListener('keydown', onKeyDown);
     $('confirmButton').addEventListener('click', onConfirm);
     $('closeButton').addEventListener('click', onConfirm);
     $('switchButton').addEventListener('click', onSwitchToExistingProfile);
     $('learnMoreLink').addEventListener('click', onLearnMore);
     if (loadTimeData.getBoolean('isSystemProfile')) {
       $('learnMoreLink').hidden = true;
     }
-    chrome.send('initializedWithSize', [document.body.scrollHeight]);
+
+    // Prefer using |document.body.offsetHeight| instead of
+    // |document.body.scrollHeight| as it returns the correct height of the
+    // even when the page zoom in Chrome is different than 100%.
+    chrome.send('initializedWithSize', [document.body.offsetHeight]);
   }
 
   function onKeyDown(e) {
     // If the currently focused element isn't something that performs an action
     // on "enter" being pressed and the user hits "enter", perform the default
     // action of the dialog, which is "OK".
     if (e.key == 'Enter' &&
         !/^(A|PAPER-BUTTON)$/.test(document.activeElement.tagName)) {
       $('confirmButton').click();
       e.preventDefault();
@@ skipping 23 matching lines @@
   }
 
   return {
     initialize: initialize,
     clearFocus: clearFocus,
     removeSwitchButton: removeSwitchButton
   };
 });
 
 document.addEventListener('DOMContentLoaded', signin.error.initialize);