[Aura] Initial app list webui.

chrome/browser/resources/shared/js/util.js

 // Copyright (c) 2011 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.
 
 /**
  * The global object.
  * @type {!Object}
  */
 const global = this;
 
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   document.onselectstart = function(e) {
     e.preventDefault();
   }
 
   // Disable dragging.
   document.ondragstart = function(e) {
     e.preventDefault();
   }
 }
 
+/**
+ * Check the directionality of the page.
+ * @return {boolean} True if Chrome is running an RTL UI.
+ */
+function isRTL() {
+  return document.documentElement.dir == 'rtl';
+}
+
+/**
+ * Simple common assertion API
+ * @param {*} condition The condition to test.  Note that this may be used to
+ *     test whether a value is defined or not, and we don't want to force a
+ *     cast to Boolean.
+ * @param {string=} opt_message A message to use in any error.
+ */
+function assert(condition, opt_message) {
+  'use strict';
+  if (!condition) {
+    var msg = 'Assertion failed';
+    if (opt_message)
+      msg = msg + ': ' + opt_message;
+    throw new Error(msg);
+  }
+}
+
+/**
+ * Get an element that's known to exist by its ID. We use this instead of just
+ * calling getElementById and not checking the result because this lets us
+ * satisfy the JSCompiler type system.
+ * @param {string} id The identifier name.
+ * @return {!Element} the Element.
+ */
+function getRequiredElement(id) {
+  var element = $(id);
+  assert(element, 'Missing required element: ' + id);
+  return element;
+}
+
 // Handle click on a link. If the link points to a chrome: or file: url, then
 // call into the browser to do the navigation.
 document.addEventListener('click', function(e) {
   // Allow preventDefault to work.
   if (!e.returnValue)
     return;
 
   var el = e.target;
   if (el.nodeType == Node.ELEMENT_NODE &&
       el.webkitMatchesSelector('A, A *')) {
     while (el.tagName != 'A') {
       el = el.parentElement;
     }
 
     if ((el.protocol == 'file:' || el.protocol == 'about:') &&
         (e.button == 0 || e.button == 1)) {
       chrome.send('navigateToUrl', [
         el.href,
         el.target,
         e.button,
         e.altKey,
         e.ctrlKey,
         e.metaKey,
         e.shiftKey
       ]);
       e.preventDefault();
     }
   }
 });