Disabled an extension test that was failing across all platforms.

PYAUTO_TESTS

 # Copyright (c) 2011 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 66 matching lines @@
       # ==================================================
       # crbug.com/83686
       '-autofill.AutofillTest.testFillProfileCrazyCharacters',
       # crbug.com/81271
       '-autofill.AutofillTest.testMergeAggregatedProfilesWithSameAddress',
       '-autofill.AutofillTest.testProfilesNotMergedWhenNoMinAddressData',
       # Browser crash when clearing browsing history and downloads together.
       # crbug.com/88128
       '-browsing_data.BrowsingDataTest.testClearHistoryAndDownloads',
       '-browsing_data.BrowsingDataTest.testClearingAccuracy',
+      # crbug.com/91764
+      '-extensions.ExtensionsTest.testSetExtensionStates',
       # Turkish I problem. crbug.com/60638
       '-find_in_page.FindMatchTests.testLocalizationAndCaseOrder',
       # crbug.com/89279
       '-gpu',
       # crbug.com/87959
       '-instant.InstantTest.testInstantLoadsFor100CharsLongQuery',
       # crbug.com/83459
       '-instant.InstantTest.testPreFetchInstantURLSetsNoCookies',
       '-omnibox.OmniboxTest.testHistoryResult',  # crbug.com/71715
       # crbug.com/91033
@@ skipping 381 matching lines @@
 
   # HTML5 media functional tests.
   'AV_FUNC': {
      'linux': [
        'media.media_event_simple_action',
        'media.media_event_simple_test',
        'media.media_event_track',
      ],
   },
 }