Add a content_settings::BaseProvider for code that is shared by all content settings providers.

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 796 matching lines @@
         'browser/content_exceptions_table_model.h',
         'browser/content_setting_bubble_model.cc',
         'browser/content_setting_bubble_model.h',
         'browser/content_setting_combo_model.cc',
         'browser/content_setting_combo_model.h',
         'browser/content_setting_image_model.cc',
         'browser/content_setting_image_model.h',
         'browser/content_settings/content_settings_details.h',
         'browser/content_settings/content_settings_pattern.cc',
         'browser/content_settings/content_settings_pattern.h',
+        'browser/content_settings/content_settings_provider.cc',
         'browser/content_settings/content_settings_provider.h',
         'browser/content_settings/host_content_settings_map.cc',
         'browser/content_settings/host_content_settings_map.h',
         'browser/content_settings/policy_content_settings_provider.cc',
         'browser/content_settings/policy_content_settings_provider.h',
         'browser/content_settings/pref_content_settings_provider.cc',
         'browser/content_settings/pref_content_settings_provider.h',
         'browser/cookies_tree_model.cc',
         'browser/cookies_tree_model.h',
         'browser/cross_site_request_manager.cc',
@@ skipping 3772 matching lines @@
       ],
     },
   ],
 }
 
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 # tab-width:2
 # indent-tabs-mode:nil
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