Disable failing tests on chromeos.

tools/telemetry/telemetry/core/backends/chrome/cros_unittest.py

 # 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.
 
 import logging
 
 from telemetry import benchmark
 from telemetry.core import exceptions
 from telemetry.core import util
 from telemetry.core.backends.chrome import cros_test_case
@@ skipping 103 matching lines @@
     self.assertTrue(self._IsScreenLocked(browser))
 
   def _UnlockScreen(self, browser):
     logging.info('Unlocking')
     browser.oobe.ExecuteJavaScript('''
         Oobe.authenticateForTesting('%s', '%s');
     ''' % (self._username, self._password))
     util.WaitFor(lambda: not browser.oobe_exists, 10)
     self.assertFalse(self._IsScreenLocked(browser))
 
-  @benchmark.Enabled('chromeos')
+  @benchmark.Disabled
   def testScreenLock(self):
     """Tests autotestPrivate.screenLock"""
     if self._is_guest:
       return
     with self._CreateBrowser(autotest_ext=True) as browser:
       self._LockScreen(browser)
       self._AttemptUnlockBadPassword(browser)
       self._UnlockScreen(browser)