Disable BackgroundTest.UseEditableState test

chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs

 // 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.
 
 // Include test fixture.
 GEN_INCLUDE(['../../testing/chromevox_next_e2e_test_base.js',
              '../../testing/assert_additions.js']);
 
 GEN_INCLUDE(['../../testing/mock_feedback.js']);
 
@@ skipping 336 matching lines @@
           .expectSpeech('Grail', 'Edit text')
           .call(color.focus.bind(color))
           .expectSpeech('Blue', 'Edit text')
           .call(name.focus.bind(name))
           .expectNextSpeechUtteranceIsNot('Blue')
           .expectSpeech('Lancelot', 'Edit text');
       mockFeedback.replay();
     }.bind(this));
 });
 
-TEST_F('BackgroundTest', 'UseEditableState', function() {
+// Flaky, see http://crbug.com/643902.
+TEST_F('BackgroundTest', 'DISABLED_UseEditableState', function() {
   this.runWithLoadedTree(
     function() {/*!
       <input type="text"></input>
       <p tabindex=0>hi</p>
     */},
     function(rootNode) {
       var assertExists = this.newCallback(function (evt) {
         assertNotNullNorUndefined(
             ChromeVoxState.desktopAutomationHandler.textEditHandler_);
         evt.stopPropagation();
@@ skipping 790 matching lines @@
     <input type="text"></input>
   */}, function(root) {
     this.listenOnce(root, 'focus', function(e) {
       var focus = ChromeVoxState.instance.currentRange.start.node;
       assertEquals(RoleType.textField, focus.role);
       assertTrue(focus.state.focused);
     });
     doCmd('nextEditText')();
   });
 });