Revert of Remove remaining window states where window is shown with opacity 0.

ash/shelf/shelf_util.h

Index: ash/shelf/shelf_util.h
diff --git a/ash/shelf/shelf_util.h b/ash/shelf/shelf_util.h
index 7e5dae17ab7363946b14344af2621001e97c7954..f4c4b80e5d8f62e1b5b7c9ce16e716b3cbd20a96 100644
--- a/ash/shelf/shelf_util.h
+++ b/ash/shelf/shelf_util.h
@@ -15,11 +15,6 @@
 
 namespace ash {
 
-// A property key to store the id of the ShelfItem associated with the window.
-extern const aura::WindowProperty<ShelfID>* const kShelfID;
-
-// A property key to store the resource id and title of the item shown on the
-// shelf for this window.
 extern const aura::WindowProperty<ShelfItemDetails*>* const
     kShelfItemDetailsKey;