Pass RepaintRects around in the functions that map rects to the repaint container.
<rdar://problem/118989146>
Pull request: https://github.com/WebKit/WebKit/pull/21111
Committed 271364@main (a56c5d7d78e0): <https://commits.webkit.org/271364@main> Reviewed commits have been landed. Closing PR #21111 and removing active labels.