Add "sidebar" section to extension manifest:...

chrome/chrome_common.gypi

 # 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.
 
 {
   'target_defaults': {
     'variables': {
       'chrome_common_target': 0,
     },
     'target_conditions': [
@@ skipping 252 matching lines @@
         'common/extensions/extension_icon_set.cc',
         'common/extensions/extension_icon_set.h',
         'common/extensions/extension_l10n_util.cc',
         'common/extensions/extension_l10n_util.h',
         'common/extensions/extension_localization_peer.cc',
         'common/extensions/extension_localization_peer.h',
         'common/extensions/extension_message_bundle.cc',
         'common/extensions/extension_message_bundle.h',
         'common/extensions/extension_resource.cc',
         'common/extensions/extension_resource.h',
+        'common/extensions/extension_sidebar_defaults.h',
+        'common/extensions/extension_sidebar_utils.cc',
+        'common/extensions/extension_sidebar_utils.h',
         'common/extensions/extension_unpacker.cc',
         'common/extensions/extension_unpacker.h',
         'common/extensions/update_manifest.cc',
         'common/extensions/update_manifest.h',
         'common/extensions/url_pattern.cc',
         'common/extensions/url_pattern.h',
         'common/extensions/user_script.cc',
         'common/extensions/user_script.h',
         'common/file_system/file_system_dispatcher.cc',
         'common/file_system/file_system_dispatcher.h',
@@ skipping 326 matching lines @@
           'configurations': {
             'Common_Base': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }