Refactor event handler classes to make it easier to add new event type listeners.

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

Index: chrome/test/data/extensions/api_test/automation/tests/tabs/attributes.js
diff --git a/chrome/test/data/extensions/api_test/automation/tests/tabs/attributes.js b/chrome/test/data/extensions/api_test/automation/tests/tabs/attributes.js
index a42184c89b4336611dc2d61a23e00038da7257ef..3c998a6621265e47f1e0a1a1fa6dc5c010884fda 100644
--- a/chrome/test/data/extensions/api_test/automation/tests/tabs/attributes.js
+++ b/chrome/test/data/extensions/api_test/automation/tests/tabs/attributes.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-var ActiveDescendantAttribute = [ 'activedescendant' ];
+var ActiveDescendantAttribute = [ 'activeDescendant' ];
 var LinkAttributes = [ 'url' ];
 var DocumentAttributes = [ 'docUrl',
                            'docTitle',
@@ -54,11 +54,11 @@ var allTests = [
 
   function testActiveDescendant() {
     var combobox = rootNode.find({ role: 'comboBox' });
-    assertTrue('activedescendant' in combobox,
+    assertTrue('activeDescendant' in combobox,
                'combobox should have an activedescendant attribute');
     var listbox = rootNode.find({ role: 'listBox' });
     var opt6 = listbox.children[5];
-    assertEq(opt6, combobox.activedescendant);
+    assertEq(opt6, combobox.activeDescendant);
     chrome.test.succeed();
   },