[SystemInfo API] Implement systemInfo.storage.onAvailableCapacityChanged event

chrome/chrome_browser_extensions.gypi

 # Copyright (c) 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.
 
 {
   'targets': [
     {
       'target_name': 'browser_extensions',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 368 matching lines @@
         'browser/extensions/api/system_info_display/display_info_provider_chromeos.cc',
         'browser/extensions/api/system_info_display/display_info_provider_mac.cc',
         'browser/extensions/api/system_info_display/display_info_provider_win.cc',
         'browser/extensions/api/system_info_display/display_info_provider_x11.cc',
         'browser/extensions/api/system_info_display/system_info_display_api.cc',
         'browser/extensions/api/system_info_display/system_info_display_api.h',
         'browser/extensions/api/system_info_memory/memory_info_provider.cc',
         'browser/extensions/api/system_info_memory/memory_info_provider.h',
         'browser/extensions/api/system_info_memory/system_info_memory_api.cc',
         'browser/extensions/api/system_info_memory/system_info_memory_api.h',
+        'browser/extensions/api/system_info_storage/storage_info_observer.h',
         'browser/extensions/api/system_info_storage/storage_info_provider.cc',
         'browser/extensions/api/system_info_storage/storage_info_provider.h',
         'browser/extensions/api/system_info_storage/storage_info_provider_linux.cc',
         'browser/extensions/api/system_info_storage/storage_info_provider_mac.cc',
         'browser/extensions/api/system_info_storage/storage_info_provider_win.cc',
         'browser/extensions/api/system_info_storage/system_info_storage_api.cc',
         'browser/extensions/api/system_info_storage/system_info_storage_api.h',
         'browser/extensions/api/tab_capture/tab_capture_api.cc',
         'browser/extensions/api/tab_capture/tab_capture_api.h',
         'browser/extensions/api/tab_capture/tab_capture_registry.cc',
@@ skipping 566 matching lines @@
           'variables': {
             'proto_in_dir': 'browser/chromeos/contacts',
             'proto_out_dir': 'chrome/browser/chromeos/contacts',
           },
           'includes': [ '../build/protoc.gypi' ]
         },
       ],
     },],  # 'chromeos=1'
   ],  # 'conditions'
 }