Before this patch, we change aDraggedItemId somewhat late in the _applyDrop method -
significantly, we do this after the aTargetNode == areaCustomizationTarget check. So
we end up bailing out before adjusting aDraggedItemId, and we add the specific dummy
item from the palette into the toolbar, rather than adding a new spring to the
toolbar, and leaving the existing palette item alone.
Simply moving this adjustment to aDraggedItemId earlier into the method is sufficient
to fix the issue at hand.
Differential Revision: https://phabricator.services.mozilla.com/D62948
--HG--
extra : moz-landing-system : lando
