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

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

 // Copyright 2016 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
  * 'site-data' handles showing the local storage summary list for all sites.
  */
 
 Polymer({
@@ skipping 57 matching lines @@
     return loadTimeData.getString('siteSettingsCookieRemoveAllShown');
   },
 
   /** @private */
   onCloseDialog_: function() {
     this.$.confirmDeleteDialog.close();
   },
 
   /**
    * Shows a dialog to confirm the deletion of multiple sites.
+   * @param {!Event} e
    * @private
    */
-  onConfirmDeleteMultipleSites_: function() {
+  onConfirmDeleteMultipleSites_: function(e) {
+    e.preventDefault();
     this.idToDelete_ = '';  // Delete all.
     this.confirmationDeleteMsg_ = loadTimeData.getString(
         'siteSettingsCookieRemoveMultipleConfirmation');
     this.$.confirmDeleteDialog.showModal();
   },
 
   /**
    * Called when deletion for a single/multiple sites has been confirmed.
    * @private
    */
@@ skipping 33 matching lines @@
 
   /**
    * @param {!{model: !{item: CookieDataSummaryItem}}} event
    * @private
    */
   onSiteTap_: function(event) {
     settings.navigateTo(settings.Route.SITE_SETTINGS_DATA_DETAILS,
         new URLSearchParams('site=' + event.model.item.site));
   },
 });