DisplayCaptureSourceCocoa::Capturer::setObserver should take a reference
<rdar://problem/108366957>
Pull request: https://github.com/WebKit/WebKit/pull/13030
Committed 263578@main (ff87cc62f746): <https://commits.webkit.org/263578@main> Reviewed commits have been landed. Closing PR #13030 and removing active labels.