Call preventDefault in all on-tap events that show a dialog.

chrome/browser/resources/settings/site_settings/site_list.js

 // Copyright 2015 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.
 
 /**
  * Enumeration mapping all possible controlled-by values for exceptions to
  * icons.
  * @enum {string}
  */
 var iconControlledBy = {
@@ skipping 199 matching lines @@
    * @param {string} source Where the setting came from.
    * @return {boolean}
    * @private
    */
   shouldShowMenu_: function(source) {
     return !(this.isExceptionControlled_(source) || this.allSites);
   },
 
   /**
    * A handler for the Add Site button.
+   * @param {!Event} e
    * @private
    */
-  onAddSiteTap_: function() {
+  onAddSiteTap_: function(e) {
+    e.preventDefault();
     var dialog = document.createElement('add-site-dialog');
     dialog.category = this.category;
     dialog.contentSetting = this.categorySubtype;
     this.shadowRoot.appendChild(dialog);
 
     dialog.open(this.categorySubtype);
 
     dialog.addEventListener('close', function() {
       dialog.remove();
     });
@@ skipping 247 matching lines @@
                 Polymer.dom(/** @type {!Event} */ (e)).localTarget));
   },
 
   /** @private */
   closeActionMenu_: function() {
     this.actionMenuSite_ = null;
     /** @type {!CrActionMenuElement} */ (
         this.$$('dialog[is=cr-action-menu]')).close();
   },
 });