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

chrome/browser/resources/settings/search_engines_page/search_engines_page.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.
 
 /**
  * @fileoverview 'settings-search-engines-page' is the settings page
  * containing search engines settings.
  */
 Polymer({
   is: 'settings-search-engines-page',
@@ skipping 50 matching lines @@
   /**
    * @param {!SearchEnginesInfo} searchEnginesInfo
    * @private
    */
   enginesChanged_: function(searchEnginesInfo) {
     this.defaultEngines = searchEnginesInfo['defaults'];
     this.otherEngines = searchEnginesInfo['others'];
     this.extensions = searchEnginesInfo['extensions'];
   },
 
-  /** @private */
-  onAddSearchEngineTap_: function() {
+  /**
+   * @param {!Event} e
+   * @private
+   */
+  onAddSearchEngineTap_: function(e) {
+    e.preventDefault();
     this.showAddSearchEngineDialog_ = true;
     this.async(function() {
       var dialog = this.$$('settings-search-engine-dialog');
       // Register listener to detect when the dialog is closed. Flip the boolean
       // once closed to force a restamp next time it is shown such that the
       // previous dialog's contents are cleared.
       dialog.addEventListener('close', function() {
         this.showAddSearchEngineDialog_ = false;
       }.bind(this));
     }.bind(this));
   },
 
   /** @private */
   computeShowExtensionsList_: function() {
     return this.extensions.length > 0;
   },
 });