shelf: Allow dragging items from main shelf to overflow shelf.

ash/shelf/shelf_view.h

Index: ash/shelf/shelf_view.h
diff --git a/ash/shelf/shelf_view.h b/ash/shelf/shelf_view.h
index e0692e103249bd6f30ad974826a738540da64d94..0c6cc3fddd7e22e01f9a6ffaf78dc6bbe3b88ae3 100644
--- a/ash/shelf/shelf_view.h
+++ b/ash/shelf/shelf_view.h
@@ -446,6 +446,9 @@ class ASH_EXPORT ShelfView : public views::View,
   // True when the icon was dragged off the shelf.
   bool dragged_off_shelf_;
 
+  // True when an item is dragged from one shelf to another (eg. overflow).
+  bool dragged_to_another_shelf_;
+
   // The rip off view when a snap back operation is underway.
   views::View* snap_back_from_rip_off_view_;
 
@@ -455,9 +458,6 @@ class ASH_EXPORT ShelfView : public views::View,
   // Holds a pointer to main ShelfView when a ShelfView is in overflow mode.
   ShelfView* main_shelf_;
 
-  // True when ripped item from overflow bubble is entered into Shelf.
-  bool dragged_off_from_overflow_to_shelf_;
-
   // True if the event is a repost event from a event which has just closed the
   // menu of the same shelf item.
   bool is_repost_event_on_same_item_;