Following the changes in bug 262691, `Element::dispatchMouseEvent` uses an out param to indicate whether an event is cancelled. This method should instead be changed to return some structure like `std::pair<bool, IsEventPreventDefaulted>` instead, and then have all callers adopt accordingly.
<rdar://problem/116859739>
Pull request: https://github.com/WebKit/WebKit/pull/18994
Committed 269266@main (b5ebe19c2491): <https://commits.webkit.org/269266@main> Reviewed commits have been landed. Closing PR #18994 and removing active labels.