Add human readable programmatic enum name/values to chrome.automation.

chrome/test/data/extensions/api_test/automation/tests/tabs/actions.js

 // Copyright 2014 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.
 
 var allTests = [
   function testSimpleAction() {
     var okButton = tree.root.firstChild().firstChild();
-    okButton.addEventListener('focus', function() {
+    okButton.addEventListener(EventType.focus, function() {
       chrome.test.succeed();
     }, true);
     okButton.focus();
   }
 ];
 
 setUpAndRunTests(allTests);