All RemoteRenderingBackends for a content process should share the IOSurfacePool
<rdar://problem/128183319>
Pull request: https://github.com/WebKit/WebKit/pull/28644
Committed 278993@main (1adb237b885b): <https://commits.webkit.org/278993@main> Reviewed commits have been landed. Closing PR #28644 and removing active labels.