<rdar://107574124> We use allocateThreadSafe for other RenderingResourceIdentifier callsites now, so the gradient ones need to match.
Pull request: https://github.com/WebKit/WebKit/pull/12341
Committed 262536@main (4c6725440012): <https://commits.webkit.org/262536@main> Reviewed commits have been landed. Closing PR #12341 and removing active labels.