Prevent overlay enter events from executing two buttons.

chrome/browser/ui/webui/options/options_browsertest.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.
 
 GEN('#include "chrome/browser/ui/webui/options/options_browsertest.h"');
 
 /**
  * Wait for the global window.onpopstate callback to be called (after a tab
  * history navigation), then execute |afterFunction|.
  */
@@ skipping 214 matching lines @@
       testDone();
     }, 0)
   }
   this.mockHandler.expects(once()).setBooleanPref(
       eq(["enable_do_not_track", false, 'Options_DoNotTrackCheckbox'])).will(
           callFunction(verifyCorrectEndState));
 
   dntCheckbox.click();
 });
 
+// Verify that preventDefault() is called on 'Enter' keydown events that trigger
+// the default button. If this doesn't happen, other elements that may get
+// focus (by the overlay closing for instance), will execute in addition to the
+// default button. See crbug.com/268336.
+TEST_F('OptionsWebUITest', 'EnterPreventsDefault', function() {
+  var page = HomePageOverlay.getInstance();
+  OptionsPage.showPageByName(page.name);
+  var event = new KeyboardEvent('keydown', {
+    'bubbles': true,
+    'cancelable': true,
+    'keyIdentifier': 'Enter'
+  });
+  assertFalse(event.defaultPrevented);
+  page.pageDiv.dispatchEvent(event);
+  assertTrue(event.defaultPrevented);
+  testDone();
+});
+
 /**
  * TestFixture for OptionsPage WebUI testing including tab history.
  * @extends {testing.Test}
  * @constructor
  */
 function OptionsWebUINavigationTest() {}
 
 OptionsWebUINavigationTest.prototype = {
   __proto__: testing.Test.prototype,
 
@@ skipping 377 matching lines @@
   var self = this;
   self.verifyOpenPages_(['settings', 'content', 'cookies']);
   self.verifyHistory_(['settings', 'languages', 'cookies'], function() {
     window.history.back();
     waitForPopstate(function() {
       self.verifyOpenPages_(['settings', 'languages']);
       testDone();
     });
   });
 });