[Extensions] Clean up renderer channel-related code

chrome/chrome_browser_extensions.gypi

 # Copyright (c) 2013 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': {
     'chrome_browser_extensions_chromeos_sources': [
       'browser/extensions/api/cast_devices_private/cast_devices_private_api.cc',
       'browser/extensions/api/cast_devices_private/cast_devices_private_api.h',
       'browser/extensions/api/certificate_provider/certificate_provider_api.cc',
@@ skipping 548 matching lines @@
       'browser/extensions/chrome_extension_function_details.cc',
       'browser/extensions/chrome_extension_function_details.h',
       'browser/extensions/chrome_extension_host_delegate.cc',
       'browser/extensions/chrome_extension_host_delegate.h',
       'browser/extensions/chrome_extension_web_contents_observer.cc',
       'browser/extensions/chrome_extension_web_contents_observer.h',
       'browser/extensions/chrome_extensions_browser_client.cc',
       'browser/extensions/chrome_extensions_browser_client.h',
       'browser/extensions/chrome_mojo_service_registration.cc',
       'browser/extensions/chrome_mojo_service_registration.h',
-      'browser/extensions/chrome_notification_observer.cc',
-      'browser/extensions/chrome_notification_observer.h',
       'browser/extensions/chrome_process_manager_delegate.cc',
       'browser/extensions/chrome_process_manager_delegate.h',
       'browser/extensions/chrome_requirements_checker.cc',
       'browser/extensions/chrome_requirements_checker.h',
       'browser/extensions/chrome_url_request_util.cc',
       'browser/extensions/chrome_url_request_util.h',
       'browser/extensions/component_extensions_whitelist/whitelist.cc',
       'browser/extensions/component_extensions_whitelist/whitelist.h',
       'browser/extensions/component_loader.cc',
       'browser/extensions/component_loader.h',
@@ skipping 557 matching lines @@
           ],
         }, {  # use_brlapi==0
           'sources': [
             'browser/extensions/api/braille_display_private/braille_controller_stub.cc',
           ],
         }],
       ],
     },
   ],
 }