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

extensions/common/permissions/api_permission.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_API_PERMISSION_H_
 #define EXTENSIONS_COMMON_PERMISSIONS_API_PERMISSION_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 143 matching lines @@
     kWebConnectable,  // for externally_connectable manifest key
     kWebNavigation,
     kWebRequest,
     kWebRequestBlocking,
     kWebRequestInternal,
     kWebRtc,
     kWebrtcAudioPrivate,
     kWebrtcLoggingPrivate,
     kWebstorePrivate,
     kWebView,
+    kScreenlockPrivate,
     kSystemCpu,
     kSystemMemory,
     kSystemInfoCpu,
     kSystemInfoMemory,
     kEnumBoundary
   };
 
   struct CheckParam {
   };
 
@@ skipping 154 matching lines @@
   const char* const name_;
   const int flags_;
   const int l10n_message_id_;
   const PermissionMessage::ID message_id_;
   const APIPermissionConstructor api_permission_constructor_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_PERMISSIONS_API_PERMISSION_H_