Enable media_seek_perf in perf_av and disable media_jerky.

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 723 matching lines @@
       'perf.ScrollTest.testBlankPageScroll',
       'perf.ScrollTest.testGooglePlusScroll',
       'perf.ScrollTest.testTextScroll',
     ],
   },
 
   # HTML5 media performance tests.
   'AV_PERF': {
      'linux': [
        'media.media_constrained_network_perf',
-       'media.media_jerky',
        'media.media_stat_perf',
+       'media.media_seek_perf',
      ],
   },
 }