Replace changes_channel with an observer list.

chrome/chrome.gyp

 # Copyright (c) 2010 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': {
     'chromium_code': 1,
 
     'variables': {
       'version_py_path': 'tools/build/version.py',
       'version_path': 'VERSION',
@@ skipping 872 matching lines @@
         'browser/sync/syncable/model_type.cc',
         'browser/sync/syncable/model_type.h',
         'browser/sync/syncable/path_name_cmp.h',
         'browser/sync/syncable/syncable-inl.h',
         'browser/sync/syncable/syncable.cc',
         'browser/sync/syncable/syncable.h',
         'browser/sync/syncable/syncable_changes_version.h',
         'browser/sync/syncable/syncable_columns.h',
         'browser/sync/syncable/syncable_id.cc',
         'browser/sync/syncable/syncable_id.h',
+        'browser/sync/util/channel.h',
         'browser/sync/util/character_set_converters.h',
         'browser/sync/util/character_set_converters_posix.cc',
         'browser/sync/util/character_set_converters_win.cc',
         'browser/sync/util/closure.h',
         'browser/sync/util/crypto_helpers.cc',
         'browser/sync/util/crypto_helpers.h',
         'browser/sync/util/dbgq.h',
         'browser/sync/util/extensions_activity_monitor.cc',
         'browser/sync/util/extensions_activity_monitor.h',
         'browser/sync/util/fast_dump.h',
@@ skipping 818 matching lines @@
       }],  # targets
     }],  # OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris"
   ],  # 'conditions'
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: