We'll need to wait for the scrolling thread to handle a wheel event before WebPageProxy continues the event processing.
<rdar://problem/105927794>
Pull request: https://github.com/WebKit/WebKit/pull/10686
Committed 260845@main (acc0a64d6511): <https://commits.webkit.org/260845@main> Reviewed commits have been landed. Closing PR #10686 and removing active labels.