[UI-side compositing] Plumb mouseEnteredContentArea and mouseExitedContentArea events to UI process
Pull request: https://github.com/WebKit/WebKit/pull/12437
<rdar://problem/107685729>
Committed 262672@main (80376d725c73): <https://commits.webkit.org/262672@main> Reviewed commits have been landed. Closing PR #12437 and removing active labels.