Remove --ash-enable-tray-dragging flag

ash/shelf/shelf_layout_manager.h

Index: ash/shelf/shelf_layout_manager.h
diff --git a/ash/shelf/shelf_layout_manager.h b/ash/shelf/shelf_layout_manager.h
index e42df4dd547ab131c0696f0b59bc08bac30dada1..7e0118a79f0dd43414e7692d28abd18edfe2ec74 100644
--- a/ash/shelf/shelf_layout_manager.h
+++ b/ash/shelf/shelf_layout_manager.h
@@ -153,14 +153,7 @@ class ASH_EXPORT ShelfLayoutManager
   // Gesture related functions:
   void OnGestureEdgeSwipe(const ui::GestureEvent& gesture);
   void StartGestureDrag(const ui::GestureEvent& gesture);
-  enum DragState {
-    DRAG_SHELF,
-    DRAG_TRAY
-  };
-  // Returns DRAG_SHELF if the gesture should continue to drag the entire shelf.
-  // Returns DRAG_TRAY if the gesture can start dragging the tray-bubble from
-  // this point on.
-  DragState UpdateGestureDrag(const ui::GestureEvent& gesture);
+  void UpdateGestureDrag(const ui::GestureEvent& gesture);
   void CompleteGestureDrag(const ui::GestureEvent& gesture);
   void CancelGestureDrag();