[visionOS] WebGL content is empty in private browsing
radar://113278323
Pull request: https://github.com/WebKit/WebKit/pull/16349
Pull request: https://github.com/WebKit/WebKit/pull/16351
Committed 266565@main (df20f33b80c9): <https://commits.webkit.org/266565@main> Reviewed commits have been landed. Closing PR #16351 and removing active labels.