OffscreenCanvas rendering (with UI-side compositing) can replace the layer contents, and hides the rendering of the border.
Pull request: https://github.com/WebKit/WebKit/pull/11988
<rdar://problem/107537962>
Committed 263731@main (d71f4ec5052b): <https://commits.webkit.org/263731@main> Reviewed commits have been landed. Closing PR #11988 and removing active labels.