mash: Migrate ShelfLockingManager to ash/common.

ash/shelf/shelf.h

Index: ash/shelf/shelf.h
diff --git a/ash/shelf/shelf.h b/ash/shelf/shelf.h
index a6fee84f7ec77f039683a7392d24b8a58413e588..fab107728e22d381cc6befc4c0cc107ae875b28d 100644
--- a/ash/shelf/shelf.h
+++ b/ash/shelf/shelf.h
@@ -11,8 +11,8 @@
 
 #include "ash/ash_export.h"
 #include "ash/common/shelf/shelf_constants.h"
+#include "ash/common/shelf/shelf_locking_manager.h"
 #include "ash/common/shelf/shelf_types.h"
-#include "ash/shelf/shelf_locking_manager.h"
 #include "ash/shelf/shelf_widget.h"
 #include "base/macros.h"
 #include "ui/gfx/geometry/size.h"
@@ -153,6 +153,10 @@ class ASH_EXPORT Shelf {
   // Returns ApplicationDragAndDropHost for this shelf.
   app_list::ApplicationDragAndDropHost* GetDragAndDropHostForAppList();
 
+  ShelfLockingManager* shelf_locking_manager_for_testing() {
+    return &shelf_locking_manager_;
+  }
+
  private:
   friend class test::ShelfTestAPI;