Update charted to 0.4.8 and roll

packages/web_components/lib/HTMLImports.js

 /**
  * @license
  * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
  * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
  * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
  * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
  * Code distributed by Google as part of the polymer project is also
  * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
  */
-// @version 0.7.21
+// @version 0.7.23
 if (typeof WeakMap === "undefined") {
   (function() {
     var defineProperty = Object.defineProperty;
     var counter = Date.now() % 1e9;
     var WeakMap = function() {
       this.name = "__st" + (Math.random() * 1e9 >>> 0) + (counter++ + "__");
     };
     WeakMap.prototype = {
       set: function(key, value) {
         var entry = key[this.name];
@@ skipping 323 matching lines @@
   };
   global.JsMutationObserver = JsMutationObserver;
   if (!global.MutationObserver) {
     global.MutationObserver = JsMutationObserver;
     JsMutationObserver._isPolyfilled = true;
   }
 })(self);
 
 (function(scope) {
   "use strict";
-  if (!window.performance) {
+  if (!(window.performance && window.performance.now)) {
     var start = Date.now();
     window.performance = {
       now: function() {
         return Date.now() - start;
       }
     };
   }
   if (!window.requestAnimationFrame) {
     window.requestAnimationFrame = function() {
       var nativeRaf = window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame;
@@ skipping 783 matching lines @@
   var rootDocument = scope.rootDocument;
   function bootstrap() {
     window.HTMLImports.importer.bootDocument(rootDocument);
   }
   if (document.readyState === "complete" || document.readyState === "interactive" && !window.attachEvent) {
     bootstrap();
   } else {
     document.addEventListener("DOMContentLoaded", bootstrap);
   }
 })(window.HTMLImports);