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<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED WONTFIX - Cannot attach Shadow root to unregistered custom element name"
href="https://bugs.webkit.org/show_bug.cgi?id=158550#c2">Comment # 2</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED WONTFIX - Cannot attach Shadow root to unregistered custom element name"
href="https://bugs.webkit.org/show_bug.cgi?id=158550">bug 158550</a>
from <span class="vcard"><a class="email" href="mailto:rniwa@webkit.org" title="Ryosuke Niwa <rniwa@webkit.org>"> <span class="fn">Ryosuke Niwa</span></a>
</span></b>
<pre>Created <span class=""><a href="attachment.cgi?id=280877" name="attach_280877" title="Reduction">attachment 280877</a> <a href="attachment.cgi?id=280877&action=edit" title="Reduction">[details]</a></span>
Reduction
It looks like this is an artifact of "contain: content". That's somehow forcing the background color to be painted behind content with a negative z-index.
You may want to file a Blink bug with this reduction (please note that the test case is BSD licensed by Apple if you were to post it on Chromium issue tracker).</pre>
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