[Chrome OS] Implement the device wallpaper policy.

components/user_manager/user.h

 // Copyright 2014 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 COMPONENTS_USER_MANAGER_USER_H_
 #define COMPONENTS_USER_MANAGER_USER_H_
 
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 60 matching lines @@
   //   (a) existing enumerated constants should never be deleted or reordered,
   //   (b) new constants should only be appended at the end of the enumeration.
   enum WallpaperType {
     DAILY = 0,         // Surprise wallpaper. Changes once a day if enabled.
     CUSTOMIZED = 1,    // Selected by user.
     DEFAULT = 2,       // Default.
     /* UNKNOWN = 3 */  // Removed.
     ONLINE = 4,        // WallpaperInfo.location denotes an URL.
     POLICY = 5,        // Controlled by policy, can't be changed by the user.
     THIRDPARTY = 6,    // Current wallpaper is set by a third party app.
-    WALLPAPER_TYPE_COUNT = 7
+    DEVICE = 7,        // Current wallpaper is the device policy controlled
+                       // wallpaper. It shows on the login screen if the device
+                       // is an enterprise managed device.
+    WALLPAPER_TYPE_COUNT = 8
   };
 
   // Returns true if user type has gaia account.
   static bool TypeHasGaiaAccount(UserType user_type);
 
   explicit User(const AccountId& account_id);
   ~User() override;
 
   // UserInfo
   std::string GetDisplayEmail() const override;
@@ skipping 215 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(User);
 };
 
 // List of known users.
 using UserList = std::vector<User*>;
 
 }  // namespace user_manager
 
 #endif  // COMPONENTS_USER_MANAGER_USER_H_