[Fallback Icons] Refactor FallbackIconService to be a BrowserContext-level singleton

chrome/chrome_browser.gypi

 # Copyright 2012 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': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 1493 matching lines @@
       'browser/sync_file_system/sync_process_runner.h',
       'browser/sync_file_system/sync_service_state.h',
       'browser/sync_file_system/sync_status_code.cc',
       'browser/sync_file_system/sync_status_code.h',
       'browser/sync_file_system/syncable_file_system_util.cc',
       'browser/sync_file_system/syncable_file_system_util.h',
       'browser/sync_file_system/task_logger.cc',
       'browser/sync_file_system/task_logger.h',
     ],
     'chrome_browser_favicon_sources': [
+      'browser/favicon/chrome_fallback_icon_client.cc',
+      'browser/favicon/chrome_fallback_icon_client.h',
+      'browser/favicon/chrome_fallback_icon_client_factory.cc',
+      'browser/favicon/chrome_fallback_icon_client_factory.h',
       'browser/favicon/chrome_favicon_client.cc',
       'browser/favicon/chrome_favicon_client.h',
       'browser/favicon/chrome_favicon_client_factory.cc',
       'browser/favicon/chrome_favicon_client_factory.h',
+      'browser/favicon/fallback_icon_service_factory.cc',
+      'browser/favicon/fallback_icon_service_factory.h',
       'browser/favicon/favicon_handler.cc',
       'browser/favicon/favicon_handler.h',
       'browser/favicon/favicon_service.cc',
       'browser/favicon/favicon_service.h',
       'browser/favicon/favicon_service_factory.cc',
       'browser/favicon/favicon_service_factory.h',
       'browser/favicon/favicon_tab_helper.cc',
       'browser/favicon/favicon_tab_helper.h',
       'browser/favicon/favicon_tab_helper_observer.h',
     ],
@@ skipping 2217 matching lines @@
           'variables': {
             'proto_in_dir': 'browser/sync_file_system/drive_backend',
             'proto_out_dir': 'chrome/browser/sync_file_system/drive_backend',
           },
           'includes': [ '../build/protoc.gypi' ]
         },
       ],
     },],
   ],
 }