mash: Migrate wallpaper controllers to ash/common.

ash/common/wallpaper/wallpaper_controller_observer.h

Index: ash/common/wallpaper/wallpaper_controller_observer.h
diff --git a/ash/wallpaper/wallpaper_controller_observer.h b/ash/common/wallpaper/wallpaper_controller_observer.h
similarity index 70%
rename from ash/wallpaper/wallpaper_controller_observer.h
rename to ash/common/wallpaper/wallpaper_controller_observer.h
index e72e6fe2904f0cc1956a97f66fbde0c664735300..2421adfd65a7478c99961bb182353fc57e629103 100644
--- a/ash/wallpaper/wallpaper_controller_observer.h
+++ b/ash/common/wallpaper/wallpaper_controller_observer.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef ASH_WALLPAPER_WALLPAPER_CONTROLLER_OBSERVER_H_
-#define ASH_WALLPAPER_WALLPAPER_CONTROLLER_OBSERVER_H_
+#ifndef ASH_COMMON_WALLPAPER_WALLPAPER_CONTROLLER_OBSERVER_H_
+#define ASH_COMMON_WALLPAPER_WALLPAPER_CONTROLLER_OBSERVER_H_
 
 #include "ash/ash_export.h"
 
@@ -20,4 +20,4 @@ class ASH_EXPORT WallpaperControllerObserver {
 
 }  // namespace ash
 
-#endif  // ASH_WALLPAPER_WALLPAPER_CONTROLLER_OBSERVER_H_
+#endif  // ASH_COMMON_WALLPAPER_WALLPAPER_CONTROLLER_OBSERVER_H_