Typecheck some of ui/webui/resources/js/ with Closure compiler.

ui/webui/resources/js/util.js

 // Copyright (c) 2012 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.
 
 <include src="assert.js">
 
 /**
- * The global object.
- * @type {!Object}
- * @const
- */
-var global = this;
-
-/**
  * Alias for document.getElementById.
  * @param {string} id The ID of the element to find.
  * @return {HTMLElement} The found element or null if not found.
  */
 function $(id) {
   return document.getElementById(id);
 }
 
 /**
  * Add an accessible message to the page that will be announced to
@@ skipping 28 matching lines @@
     global[callbackName] = old;
 
     var args = Array.prototype.slice.call(arguments);
     return callback.apply(global, args);
   };
   chrome.send(name, params);
 }
 
 /**
  * Returns the scale factors supported by this platform.
- * @return {array} The supported scale factors.
+ * @return {Array} The supported scale factors.
  */
 function getSupportedScaleFactors() {
   var supportedScaleFactors = [];
   if (cr.isMac || cr.isChromeOS) {
     supportedScaleFactors.push(1);
     supportedScaleFactors.push(2);
   } else {
     // Windows must be restarted to display at a different scale factor.
     supportedScaleFactors.push(window.devicePixelRatio);
   }
@@ skipping 16 matching lines @@
     // Add a space to work around the WebKit bug.
     s2 += ' ';
   }
   return 'url("' + s2 + '")';
 }
 
 /**
  * Returns the URL of the image, or an image set of URLs for the profile avatar.
  * Default avatars have resources available for multiple scalefactors, whereas
  * the GAIA profile image only comes in one size.
-
- * @param {string} url The path of the image.
+ *
+ * @param {string} path The path of the image.
  * @return {string} The url, or an image set of URLs of the avatar image.
  */
 function getProfileAvatarIcon(path) {
   var chromeThemePath = 'chrome://theme';
   var isDefaultAvatar =
       (path.slice(0, chromeThemePath.length) == chromeThemePath);
   return isDefaultAvatar ? imageset(path + '@scalefactorx'): url(path);
 }
 
 /**
@@ skipping 21 matching lines @@
     s += url(pathWithScaleFactor) + ' ' + scaleFactor + 'x';
 
     if (i != supportedScaleFactors.length - 1)
       s += ', ';
   }
   return '-webkit-image-set(' + s + ')';
 }
 
 /**
  * Parses query parameters from Location.
- * @param {string} location The URL to generate the CSS url for.
- * @return {object} Dictionary containing name value pairs for URL
+ * @param {Location} location The URL to generate the CSS url for.
+ * @return {Object} Dictionary containing name value pairs for URL
  */
 function parseQueryParams(location) {
   var params = {};
   var query = unescape(location.search.substring(1));
   var vars = query.split('&');
   for (var i = 0; i < vars.length; i++) {
     var pair = vars[i].split('=');
     params[pair[0]] = pair[1];
   }
   return params;
 }
 
 /**
  * Creates a new URL by appending or replacing the given query key and value.
  * Not supporting URL with username and password.
- * @param {object} location The original URL.
+ * @param {Location} location The original URL.
  * @param {string} key The query parameter name.
  * @param {string} value The query parameter value.
  * @return {string} The constructed new URL.
  */
 function setQueryParam(location, key, value) {
   var query = parseQueryParams(location);
   query[encodeURIComponent(key)] = encodeURIComponent(value);
 
   var newQuery = '';
   for (var q in query) {
     newQuery += (newQuery ? '&' : '?') + q + '=' + query[q];
   }
 
   return location.origin + location.pathname + newQuery + location.hash;
 }
 
+/**
+ * @param {Node} el An element to search for ancestors with |className|.
+ * @param {string} className A class to search for.
+ * @return {Node} A node with class of |className| or null if none is found.
+ */
 function findAncestorByClass(el, className) {
   return findAncestor(el, function(el) {
-    if (el.classList)
-      return el.classList.contains(className);
-    return null;
+    return el.classList && el.classList.contains(className);
   });
 }
 
 /**
  * Return the first ancestor for which the {@code predicate} returns true.
  * @param {Node} node The node to check.
- * @param {function(Node) : boolean} predicate The function that tests the
+ * @param {function(Node):boolean} predicate The function that tests the
  *     nodes.
  * @return {Node} The found ancestor or null if not found.
  */
 function findAncestor(node, predicate) {
   var last = false;
   while (node != null && !(last = predicate(node))) {
     node = node.parentNode;
   }
   return last ? node : null;
 }
@@ skipping 30 matching lines @@
       e.preventDefault();
   };
 }
 
 /**
  * Call this to stop clicks on <a href="#"> links from scrolling to the top of
  * the page (and possibly showing a # in the link).
  */
 function preventDefaultOnPoundLinkClicks() {
   document.addEventListener('click', function(e) {
-    var anchor = findAncestor(e.target, function(el) {
+    var anchor = findAncestor(/** @type {Node} */(e.target), function(el) {
       return el.tagName == 'A';
     });
     // Use getAttribute() to prevent URL normalization.
     if (anchor && anchor.getAttribute('href') == '#')
       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';
 }
 
 /**
  * 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;
+  return /** @type {!Element} */(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) {
   if (e.defaultPrevented)
     return;
 
   var el = e.target;
   if (el.nodeType == Node.ELEMENT_NODE &&
@@ skipping 159 matching lines @@
  * @param {number} maxLength The maximum length allowed for the string.
  * @return {string} The original string if its length does not exceed
  *     |maxLength|. Otherwise the first |maxLength| - 1 characters with '...'
  *     appended.
  */
 function elide(original, maxLength) {
   if (original.length <= maxLength)
     return original;
   return original.substring(0, maxLength - 1) + '\u2026';
 }