Restore to user selected wallpaper after browser crash

ash/shell_delegate.h

Index: ash/shell_delegate.h
diff --git a/ash/shell_delegate.h b/ash/shell_delegate.h
index 8e9076e6465f7578140728966ff00104b9e748a8..4b4a6f06700b7298385dd8d1ad50f0542a21cdb8 100644
--- a/ash/shell_delegate.h
+++ b/ash/shell_delegate.h
@@ -30,6 +30,7 @@ struct LauncherItem;
 class ScreenshotDelegate;
 class SystemTray;
 class SystemTrayDelegate;
+class UserWallpaperDelegate;
 
 // Delegate of the Shell.
 class ASH_EXPORT ShellDelegate {
@@ -80,6 +81,9 @@ class ASH_EXPORT ShellDelegate {
 
   // Creates a system-tray delegate. Shell takes ownership of the delegate.
   virtual SystemTrayDelegate* CreateSystemTrayDelegate(SystemTray* tray) = 0;
+
+  // Creates a user wallpaper delegate. Shell takes ownership of the delegate.
+  virtual UserWallpaperDelegate* CreateUserWallpaperDelegate() = 0;
 };
 
 }  // namespace ash