When the "progress" attribute is "0", we should show a placeholder with the arrow-down-circle symbol. rdar://108266781
Pull request: https://github.com/WebKit/WebKit/pull/13435
Committed 263696@main (1f2261656aa2): <https://commits.webkit.org/263696@main> Reviewed commits have been landed. Closing PR #13435 and removing active labels.