The chrome.screenlockPrivate API allows select apps to control the ChromeOS ScreenLocker.

extensions/common/permissions/permission_message.h

 // Copyright 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.
 
 #ifndef EXTENSIONS_COMMON_PERMISSIONS_PERMISSION_MESSAGE_H_
 #define EXTENSIONS_COMMON_PERMISSIONS_PERMISSION_MESSAGE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 60 matching lines @@
     kDeclarativeWebRequest,
     kFileSystemDirectory,
     kFileSystemWriteDirectory,
     kSignedInDevices,
     kWallpaper,
     kNetworkState,
     kHomepage,
     kSearchProvider,
     kStartupPages,
     kMediaGalleriesAllGalleriesDelete,
+    kScreenlockPrivate,
     kEnumBoundary,
   };
   COMPILE_ASSERT(PermissionMessage::kNone > PermissionMessage::kUnknown,
                  kNone_not_greater_than_kUnknown);
 
   // Creates the corresponding permission message.
   PermissionMessage(ID id, const string16& message);
   PermissionMessage(ID id, const string16& message, const string16& details);
   ~PermissionMessage();
 
@@ skipping 23 matching lines @@
   ID id_;
   string16 message_;
   string16 details_;
 };
 
 typedef std::vector<PermissionMessage> PermissionMessages;
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_PERMISSIONS_PERMISSION_MESSAGE_H_