mash: Migrate ShelfLockingManager to ash/common.

ash/common/shelf/wm_shelf.h

Index: ash/common/shelf/wm_shelf.h
diff --git a/ash/common/shelf/wm_shelf.h b/ash/common/shelf/wm_shelf.h
index 0aa65780a07e9ed6df3609fdfeb19315e8c25c02..763f417ab190e608088f4f4b5c5181255d5d535b 100644
--- a/ash/common/shelf/wm_shelf.h
+++ b/ash/common/shelf/wm_shelf.h
@@ -19,6 +19,7 @@ class MouseEvent;
 
 namespace ash {
 
+class ShelfLockingManager;
 class WmShelfObserver;
 class WmWindow;
 
@@ -91,6 +92,8 @@ class ASH_EXPORT WmShelf {
   // Simulates a virtual keyboard bounds update.
   virtual void SetKeyboardBoundsForTesting(const gfx::Rect& bounds) = 0;
 
+  virtual ShelfLockingManager* GetShelfLockingManagerForTesting() = 0;
+
  protected:
   virtual ~WmShelf() {}
 };