[MacViews] Fix Drag and Drop bugs

ui/base/dragdrop/drag_drop_types_mac.mm

Index: ui/base/dragdrop/drag_drop_types_mac.mm
diff --git a/ui/base/dragdrop/drag_drop_types_mac.mm b/ui/base/dragdrop/drag_drop_types_mac.mm
index 0c1d340c52150e40e4d0f503f531d066da7f77e6..dd0226e29fc4475e8ad64c6e9efd00d0b1a407ec 100644
--- a/ui/base/dragdrop/drag_drop_types_mac.mm
+++ b/ui/base/dragdrop/drag_drop_types_mac.mm
@@ -21,4 +21,18 @@ uint64_t ui::DragDropTypes::DragOperationToNSDragOperation(int drag_operation) {
   return ns_drag_operation;
 }
 
+int ui::DragDropTypes::NSDragOperationToDragOperation(
+    uint64_t ns_drag_operation) {
+  NSUInteger drag_operation = DRAG_NONE;
+
+  if (ns_drag_operation & NSDragOperationLink)
+    drag_operation |= DRAG_LINK;
+  if (ns_drag_operation & NSDragOperationCopy)
+    drag_operation |= DRAG_COPY;
+  if (ns_drag_operation & NSDragOperationMove)
+    drag_operation |= DRAG_MOVE;
+
+  return drag_operation;
+}
+
 }  // namespace ui