Add support for favicon scale factor in WebUI

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

Index: chrome/browser/resources/shared/js/util.js
diff --git a/chrome/browser/resources/shared/js/util.js b/chrome/browser/resources/shared/js/util.js
index 1a927d1a6ee7f768a79cbc80b166090f9afeb2b3..2d75ea2e6184a437d5afdcc19d09bfc9ac63eb36 100644
--- a/chrome/browser/resources/shared/js/util.js
+++ b/chrome/browser/resources/shared/js/util.js
@@ -226,3 +226,15 @@ function appendParam(url, key, value) {
     return url + '?' + param;
   return url + '&' + param;
 }
+
+/**
+ * Creates a new URL for a favicon request.
+ * @param {string} url The url for the favicon.
+ * @param {number=} opt_size Optional preferred size of the favicon.
+ * @return {string} Updated URL for the favicon.
+ */
+function getFaviconURL(url, opt_size) {
+  var size = opt_size || 16;
+  return 'chrome://favicon/size/' + size + '@' +
+      window.devicePixelRatio + 'x/' + url;
+}