Add screen rotation animator lock.

ash/wallpaper/wallpaper_controller.h

Index: ash/wallpaper/wallpaper_controller.h
diff --git a/ash/wallpaper/wallpaper_controller.h b/ash/wallpaper/wallpaper_controller.h
index e72991f205552ffeb437880e421d59213a960ffa..d3932d10f6c661990480b4a3989cf22f349bed6f 100644
--- a/ash/wallpaper/wallpaper_controller.h
+++ b/ash/wallpaper/wallpaper_controller.h
@@ -33,6 +33,7 @@ class WallpaperResizer;
 
 namespace ash {
 
+class ScreenRotationAnimatorLock;
 class WallpaperControllerObserver;
 
 // Controls the desktop background wallpaper:
@@ -117,6 +118,11 @@ class ASH_EXPORT WallpaperController
   // Opens the set wallpaper page in the browser.
   void OpenSetWallpaperPage();
 
+  // ScreenRotationAnimatorLock controllered by the ScreenRotationAnimator.
+  void SetScreenRotationAnimatorLock(ScreenRotationAnimatorLock* lock) {
+    screen_rotation_animator_lock_ = lock;
+  }
+
   // mojom::WallpaperController overrides:
   void SetWallpaperPicker(mojom::WallpaperPickerPtr picker) override;
   void SetWallpaper(const SkBitmap& wallpaper,
@@ -204,6 +210,9 @@ class ASH_EXPORT WallpaperController
 
   ScopedSessionObserver scoped_session_observer_;
 
+  // weak ptr.
+  ScreenRotationAnimatorLock* screen_rotation_animator_lock_;
+
   DISALLOW_COPY_AND_ASSIGN(WallpaperController);
 };