Drag actions currently send a separate IPC call to notify the UI process that they have been handled. We should use completion handlers instead.
<rdar://problem/117665237>
Pull request: https://github.com/WebKit/WebKit/pull/19700
Committed 269965@main (b7a48dcd4cf2): <https://commits.webkit.org/269965@main> Reviewed commits have been landed. Closing PR #19700 and removing active labels.