STR: 1) Enable webcomponents 2) Open attached test case 3) click within iframe 4) try to scroll with arrow keys Expected: The iframe is focused and the page scrolls Actual: The iframe doesn't scroll Note: If I use a regular element instead an iframe it becomes correctly focused.

Seems the following will fix it: +++ b/dom/base/nsContentUtils.cpp @@ -6148,7 +6148,7 @@ nsContentUtils::IsSubDocumentTabbable(nsIContent* aContent) { //XXXsmaug Shadow DOM spec issue! // We may need to change this to GetComposedDoc(). - nsIDocument* doc = aContent->GetUncomposedDoc(); + nsIDocument* doc = aContent->GetComposedDoc(); if (!doc) { return false; }

(I'm surprised anyone using the old v0 shadow DOM. But perhaps converting to the new slots based shadow DOM v1 won't be that hard when it becomes available. )

FWIW, we're using it in positron.

I see. That patch btw makes totally sense :) I don't recall if the spec has been fixed in this case though. So whoever reviews the patch needs to review the spec too and if it is still buggy, file a spec bug. I hope positron can later move to use the new syntax quite easily.

I'm interested in William's thoughts here.