The threaded compositor is already attached to a WebPage so we can notify the associated scrolling tree directly instead of iterating all scrolling trees in the process. Also accessing the WebProcess and EventDipatcher from ThreadedCompositor was a layering violation.
Pull request: https://github.com/WebKit/WebKit/pull/5702
Committed 255913@main (8bc5773a96b5): <https://commits.webkit.org/255913@main> Reviewed commits have been landed. Closing PR #5702 and removing active labels.