[giow] (3) Make sure that if you cancel a drag-and-drop operation, we reset the current drag operation to 'none' so that you can tell in the dragend event.
Affected topics: HTML

git-svn-id: http://svn.whatwg.org/webapps@8143 340c8d12-0b0e-0410-8428-c7bf67bfef74