Update behavior of one-click infobar to remove modal dialog, add "undo".

chrome/test/functional/PYAUTO_TESTS

 # 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.
 #
 # This file lists the pyauto tests that run as a part of the functional test
 # suite.
 #
 # Tests can be enabled on a per-platform basis. Tests not listed here will
 # not be run.
 #
@@ skipping 67 matching lines @@
       'pyauto_webdriver',
       'search_engines',
       'shortcuts',
       'special_tabs',
       'sync.SyncTest',
       'test_basic',
       'test_pyauto',
       'themes',
       'youtube',
 
-      # One-click infobars disabled on M20 by r135749.
-      # Re-enable for M21 after branch point.
-      '-infobars.OneClickInfobarTest',
-
       # ==================================================
       # Disabled tests that need to be investigated/fixed.
       # ==================================================
       # crbug.com/102798
       '-autofill.AutofillTest.testMergeAggregatedProfilesWithSameAddress',
       # crbug.com/99475
       '-autofill.AutofillTest.testNoDuplicatePhoneNumsInPrefs',
       # crbug.com/123396
       '-fullscreen_mouselock.FullscreenMouselockTest.testPatternsForFSAndML',
       # crbug.com/100593
@@ skipping 634 matching lines @@
 
   # WebRTC MediaStream tests. Requires webcam and audio device to be present on
   # the test machine.
   'WEBRTC': {
     'all': [
       'media_stream_infobar',
       'webrtc_call',
     ],
   },
 }