We currently prewarm a Web process when the main frame load has finished. Instead, prewarm a Web process when the provisional load starts, which has been measured to be a 1-2% speedup in page load time.
<rdar://problem/112777207>
Pull request: https://github.com/WebKit/WebKit/pull/16039
Committed 266255@main (a7685646bede): <https://commits.webkit.org/266255@main> Reviewed commits have been landed. Closing PR #16039 and removing active labels.