Add IDL and stub implementation for chrome.usersPrivate API.

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/enterprise_platform_keys/enterprise_platform_keys_api.cc',
       'browser/extensions/api/enterprise_platform_keys/enterprise_platform_keys_api.h',
       'browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.cc',
@@ skipping 469 matching lines @@
       'browser/extensions/api/tabs/tabs_event_router.cc',
       'browser/extensions/api/tabs/tabs_event_router.h',
       'browser/extensions/api/tabs/tabs_windows_api.cc',
       'browser/extensions/api/tabs/tabs_windows_api.h',
       'browser/extensions/api/tabs/windows_event_router.cc',
       'browser/extensions/api/tabs/windows_event_router.h',
       'browser/extensions/api/tabs/windows_util.cc',
       'browser/extensions/api/tabs/windows_util.h',
       'browser/extensions/api/top_sites/top_sites_api.cc',
       'browser/extensions/api/top_sites/top_sites_api.h',
+      'browser/extensions/api/users_private/users_private_api.cc',
+      'browser/extensions/api/users_private/users_private_api.h',
       'browser/extensions/api/web_navigation/frame_navigation_state.cc',
       'browser/extensions/api/web_navigation/frame_navigation_state.h',
       'browser/extensions/api/web_navigation/web_navigation_api.cc',
       'browser/extensions/api/web_navigation/web_navigation_api.h',
       'browser/extensions/api/web_navigation/web_navigation_api_constants.cc',
       'browser/extensions/api/web_navigation/web_navigation_api_constants.h',
       'browser/extensions/api/web_navigation/web_navigation_api_helpers.cc',
       'browser/extensions/api/web_navigation/web_navigation_api_helpers.h',
       'browser/extensions/api/web_request/chrome_extension_web_request_event_router_delegate.cc',
       'browser/extensions/api/web_request/chrome_extension_web_request_event_router_delegate.h',
@@ skipping 593 matching lines @@
           ],
         }, {  # use_brlapi==0
           'sources': [
             'browser/extensions/api/braille_display_private/braille_controller_stub.cc',
           ],
         }],
       ],
     },
   ],
 }