Fix Crash in DragDropClientMac::Drop()

ui/views/cocoa/drag_drop_client_mac.mm

Index: ui/views/cocoa/drag_drop_client_mac.mm
diff --git a/ui/views/cocoa/drag_drop_client_mac.mm b/ui/views/cocoa/drag_drop_client_mac.mm
index 9dda333f01be43f1580fc022315501b8f7f162ef..d637f5d9e37ee98f47af4cd3853993224b3ca5e6 100644
--- a/ui/views/cocoa/drag_drop_client_mac.mm
+++ b/ui/views/cocoa/drag_drop_client_mac.mm
@@ -148,11 +148,15 @@ NSDragOperation DragDropClientMac::DragUpdate(id<NSDraggingInfo> sender) {
 }
 
 NSDragOperation DragDropClientMac::Drop(id<NSDraggingInfo> sender) {
-  int drag_operation = drop_helper_.OnDrop(
-      *[data_source_ data], LocationInView([sender draggingLocation]),
-      operation_);
+  // OnDrop can optionally delete |this|, so clear data members first.
+  base::scoped_nsobject<CocoaDragDropDataProvider> data_source = data_source_;
+  int operation = operation_;
   data_source_.reset();
   operation_ = 0;
+
+  int drag_operation = drop_helper_.OnDrop(
+      *[data_source data], LocationInView([sender draggingLocation]),
+      operation);
   return ui::DragDropTypes::DragOperationToNSDragOperation(drag_operation);
 }