Created attachment 578784 [details] [diff] [review]
We can use the datatransfer for what it needs.
Comment on attachment 578784 [details] [diff] [review]
nsIDOMDataTransfer has no method named GetDropEffectInt yet.
r=me with that fixed.
>+ // True while dragging over the tree.
>+ bool mIsDragging;
This belongs with mDropAllowed (for packing).