mus drag and drop: return the completed effect to the caller.

services/ui/ws/drag_controller.h

Index: services/ui/ws/drag_controller.h
diff --git a/services/ui/ws/drag_controller.h b/services/ui/ws/drag_controller.h
index 1cd7d3ad4da13d7a207b61551b1db6521e1be74f..3b781a44a2ebb43d2732ace7123f3f62b912b5e7 100644
--- a/services/ui/ws/drag_controller.h
+++ b/services/ui/ws/drag_controller.h
@@ -52,7 +52,7 @@ class DragController : public ServerWindowObserver {
 
   // Notifies all windows we messaged that the drag is finished, and then tell
   // |source| the result.
-  void MessageDragCompleted(bool success);
+  void MessageDragCompleted(bool success, uint32_t action_taken);
 
   // Returns the number of events on |window|. A value of 1 means that there's
   // a single event outstanding that we're waiting for a response from the
@@ -77,7 +77,7 @@ class DragController : public ServerWindowObserver {
 
   // Callback methods.
   void OnDragStatusCompleted(const WindowId& id, uint32_t bitmask);
-  void OnDragDropCompleted(const WindowId& id, uint32_t bitmask);
+  void OnDragDropCompleted(const WindowId& id, uint32_t action);
 
   // ServerWindowObserver:
   void OnWindowDestroying(ServerWindow* window) override;