Get rid of extensions dependency from content\browser.

chrome/chrome_browser.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.
 
 {
   'targets': [
     {
       'target_name': 'browser',
       'type': '<(library)',
       'msvs_guid': '5BF908A7-68FB-4A4B-99E3-8C749F1FE4EA',
@@ skipping 954 matching lines @@
         'browser/extensions/extension_rlz_module.cc',
         'browser/extensions/extension_rlz_module.h',
         'browser/extensions/extension_service.cc',
         'browser/extensions/extension_service.h',
         'browser/extensions/extension_sidebar_api.cc',
         'browser/extensions/extension_sidebar_api.h',
         'browser/extensions/extension_special_storage_policy.cc',
         'browser/extensions/extension_special_storage_policy.h',
         'browser/extensions/extension_tab_id_map.cc',
         'browser/extensions/extension_tab_id_map.h',
+        'browser/extensions/extension_tab_helper.cc',
+        'browser/extensions/extension_tab_helper.h',
         'browser/extensions/extension_tabs_module.cc',
         'browser/extensions/extension_tabs_module.h',
         'browser/extensions/extension_tabs_module_constants.cc',
         'browser/extensions/extension_tabs_module_constants.h',
         'browser/extensions/extension_test_api.cc',
         'browser/extensions/extension_test_api.h',
         'browser/extensions/extension_toolbar_model.cc',
         'browser/extensions/extension_toolbar_model.h',
         'browser/extensions/extension_tts_api.cc',
         'browser/extensions/extension_tts_api.h',
@@ skipping 3415 matching lines @@
       'hard_dependency': 1,
     },
   ],
 }
 
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