mash: Port mojo:ash_sysui's ContextMenuMus to mojo:ash.

ash/common/shell_delegate.h

Index: ash/common/shell_delegate.h
diff --git a/ash/common/shell_delegate.h b/ash/common/shell_delegate.h
index 9a46959ecfdb8c237ffe439989505d12bca1ea28..16f905c55ac6ed0d59376474a833436f109dabc2 100644
--- a/ash/common/shell_delegate.h
+++ b/ash/common/shell_delegate.h
@@ -46,8 +46,8 @@ class SessionStateDelegate;
 class ShelfDelegate;
 class ShelfModel;
 class SystemTrayDelegate;
-class UserWallpaperDelegate;
 struct ShelfItem;
+class WallpaperDelegate;
 class WmShelf;
 class WmWindow;
 
@@ -108,8 +108,8 @@ class ASH_EXPORT ShellDelegate {
   // Creates a system-tray delegate. Shell takes ownership of the delegate.
   virtual SystemTrayDelegate* CreateSystemTrayDelegate() = 0;
 
-  // Creates a user wallpaper delegate. Shell takes ownership of the delegate.
-  virtual UserWallpaperDelegate* CreateUserWallpaperDelegate() = 0;
+  // Creates a wallpaper delegate. Shell takes ownership of the delegate.
+  virtual std::unique_ptr<WallpaperDelegate> CreateWallpaperDelegate() = 0;
 
   // Creates a session state delegate. Shell takes ownership of the delegate.
   virtual SessionStateDelegate* CreateSessionStateDelegate() = 0;