Polish the SystemInfoProvider template code and refactor StorageInfoProvider based on it

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 229 matching lines @@
         'browser/extensions/api/socket/udp_socket.h',
         'browser/extensions/api/system_info_cpu/cpu_info_provider_mac.cc',
         'browser/extensions/api/system_info_cpu/cpu_info_provider_linux.cc',
         'browser/extensions/api/system_info_cpu/cpu_info_provider_win.cc',
         'browser/extensions/api/system_info_cpu/system_info_cpu_api.cc',
         'browser/extensions/api/system_info_cpu/system_info_cpu_api.h',
         '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/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/tabs/execute_code_in_tab_function.cc',
         'browser/extensions/api/tabs/execute_code_in_tab_function.h',
         'browser/extensions/api/tabs/tabs.cc',
         'browser/extensions/api/tabs/tabs.h',
         'browser/extensions/api/tabs/tabs_constants.cc',
         'browser/extensions/api/tabs/tabs_constants.h',
         'browser/extensions/api/terminal/terminal_extension_helper.cc',
         'browser/extensions/api/terminal/terminal_extension_helper.h',
         'browser/extensions/api/terminal/terminal_private_api.cc',
@@ skipping 517 matching lines @@
           'sources': [
             'browser/extensions/app_host.rc',
             'browser/extensions/app_host_stub_main.cc',
           ],
         },
       ],
     }, ],  # 'OS=="win"'
   ],  # 'conditions'
 }