[Signin Error Dialog] (1/3) Added necessary web components

chrome/browser/resources/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 onConfirm(e) {
+    chrome.send('confirm');
+  }
+
+  function onSwitchToExistingProfile(e) {
+    chrome.send('switchToExistingProfile');
+  }
+
+  function onLearnMore(e) {
+    chrome.send('learnMore');
+  }
+
+  function initialize() {
+    document.addEventListener('keydown', onKeyDown);
+    $('primaryConfirmButton').addEventListener('click', onConfirm);
+    $('secondaryConfirmButton').addEventListener('click', onConfirm);
+    $('switchButton').addEventListener('click', onSwitchToExistingProfile);
+    $('learnMoreLink').addEventListener('click', onLearnMore);
+    chrome.send('initializedWithSize', [document.body.scrollHeight]);
+  }
+
+  function clearFocus() {

[tommycli, 2016/08/24 17:22:52]

Can we confirm that this is still needed? Esp. if it's still required to be
called from the C++ side after the initialize() method?

[Jane, 2016/08/25 16:35:29]

Confirmed that on mac, the "Learn more" link would be automatically focused
every time the dialog loads up.

+    document.activeElement.blur();
+  }
+
+  function onKeyDown(e) {

[tommycli, 2016/08/24 17:22:52]

nit: would be good to make the order of these functions same as how they're
added in the initialize() method.

Also, it seems like it would be better to just set the default focus to the
desired button, rather than add a document level input handler.

[Jane, 2016/08/25 16:35:29]

Done nit.
I talked to anthonyvd@ who did this for sync-confirmation, and his original idea
of setting default focus to the desired button was shot down by dbeam@ because
of screenreader messups, hence the workaround (see
https://codereview.chromium.org/1949613003). What do you think?

+    // 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)) {
+      $('primaryConfirmButton').click();
+      e.preventDefault();
+    }
+  }
+
+  function removeSwitchButton() {
+    $('switchButton').style.display = 'none';
+    $('secondaryConfirmButton').style.display = 'none';
+    $('primaryConfirmButton').style.display = '';
+  }
+
+  return {
+    clearFocus: clearFocus,
+    initialize: initialize,
+    removeSwitchButton: removeSwitchButton
+  };
+});
+
+document.addEventListener('DOMContentLoaded', signin.error.initialize);