Gracefully handle mismatched drag ended notifications.

Should the embedder end up signalling the end of a drag operation
via EventHandler::dragSourceEndedAt(), but Blink has initiated
another drag operation, for whatever reason or source, then catch
this and gracefully bail.

R=jochen,rbyers
BUG=445308

Review URL: https://codereview.chromium.org/839253002

git-svn-id: svn://svn.chromium.org/blink/trunk@188256 bbb929c8-8fbe-4397-9dbb-9b2b20218538
3 files changed
tree: c055182244dab1e22bab6ed12ab8e3649aa91fb4
  1. third_party/