Update charted to 0.4.8 and roll

packages/web_components/lib/HTMLImports.js

Index: packages/web_components/lib/HTMLImports.js
diff --git a/packages/web_components/lib/HTMLImports.js b/packages/web_components/lib/HTMLImports.js
old mode 100644
new mode 100755
index 047e5ac32691bf13b61eb326bc1341f2e7169c1b..39c2d6aef840f4b6677419f0f9177569ae1246e2
--- a/packages/web_components/lib/HTMLImports.js
+++ b/packages/web_components/lib/HTMLImports.js
@@ -7,7 +7,7 @@
  * 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;
@@ -351,7 +351,7 @@ if (typeof WeakMap === "undefined") {
 
 (function(scope) {
   "use strict";
-  if (!window.performance) {
+  if (!(window.performance && window.performance.now)) {
     var start = Date.now();
     window.performance = {
       now: function() {