Add IDL and stub implementation for chrome.usersPrivate API.

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 90 matching lines @@
     kHosts2ReadOnly,
     kHosts3ReadOnly,
     kHosts4OrMoreReadOnly,
     kHostsAllReadOnly,
     kInterceptAllKeys,
     kSettingsPrivate,
     kPrinterProvider,
     kSearchEnginesPrivate,
     kAutofillPrivate,
     kPasswordsPrivate,
+    kUsersPrivate,
     // Last entry: Add new entries above and ensure to update the
     // "ExtensionPermission2" enum in tools/metrics/histograms/histograms.xml
     // (by running update_extension_permission.py).
     kEnumBoundary,
   };
   static_assert(PermissionMessage::kNone > PermissionMessage::kUnknown,
                 "kNone should not greater than kUnknown");
 
   // Creates the corresponding permission message.
   PermissionMessage(ID id, const base::string16& message);
@@ skipping 29 matching lines @@
   base::string16 message_;
   base::string16 details_;
 };
 
 typedef std::vector<PermissionMessage> PermissionMessages;
 typedef std::vector<PermissionMessage::ID> PermissionMessageIDs;
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_PERMISSIONS_PERMISSION_MESSAGE_H_