[extensions] Don't let clicks on <a href="#"> links escape un-prevented.

chrome/browser/resources/shared/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.
 
 /**
  * The global object.
  * @type {!Object}
  * @const
  */
 var global = this;
@@ skipping 111 matching lines @@
   };
 
   // Disable dragging.
   document.ondragstart = function(e) {
     if (!(opt_allowDragStart && opt_allowDragStart.call(this, e)))
       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) {
+    if (e.target.nodeName == 'A' && e.target.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';
 }
 
 /**
  * Simple common assertion API
  * @param {*} condition The condition to test.  Note that this may be used to
@@ skipping 62 matching lines @@
  * @param {string} value The value of the param.
  * @return {string} The new URL.
  */
 function appendParam(url, key, value) {
   var param = encodeURIComponent(key) + '=' + encodeURIComponent(value);
 
   if (url.indexOf('?') == -1)
     return url + '?' + param;
   return url + '&' + param;
 }