[Sync] Move some code into new class JsMutationEventObserver

chrome/chrome_tests.gypi

 # 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.
 
 {
   'variables' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
@@ skipping 2913 matching lines @@
         'browser/sync/engine/sync_scheduler_whitebox_unittest.cc',
         'browser/sync/engine/syncer_unittest.cc',
         'browser/sync/engine/syncproto_unittest.cc',
         'browser/sync/engine/verify_updates_command_unittest.cc',
         'browser/sync/internal_api/change_record_unittest.cc',
         'browser/sync/internal_api/syncapi_mock.h',
         'browser/sync/internal_api/syncapi_server_connection_manager_unittest.cc',
         'browser/sync/internal_api/syncapi_unittest.cc',
         'browser/sync/js/js_arg_list_unittest.cc',
         'browser/sync/js/js_event_details_unittest.cc',
+        'browser/sync/js/js_mutation_event_observer_unittest.cc',
         'browser/sync/js/js_sync_manager_observer_unittest.cc',
         'browser/sync/notifier/cache_invalidation_packet_handler_unittest.cc',
         'browser/sync/notifier/chrome_invalidation_client_unittest.cc',
         'browser/sync/notifier/chrome_system_resources_unittest.cc',
         'browser/sync/notifier/invalidation_notifier_unittest.cc',
         'browser/sync/notifier/non_blocking_invalidation_notifier_unittest.cc',
         'browser/sync/notifier/p2p_notifier_unittest.cc',
         'browser/sync/notifier/registration_manager_unittest.cc',
         'browser/sync/profile_sync_factory_mock.h',
         'browser/sync/protocol/proto_enum_conversions_unittest.cc',
@@ skipping 976 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],  # 'coverage!=0'
   ],  # 'conditions'
 }