Our user agent quirk to make YouTube 360 work breaks the new YouTube UI, causing it to attempt to use the obsolete custom elements v0 API. WebKit only supports the v1 API. We have to remove this quirk. Note this does not affect Safari as Apple ports don't use our user agent quirks.
Created attachment 308908 [details] Patch
""" This preview is closed... for now Thanks for your interest in helping us with the new desktop design! We've got a ton of feedback we're reading through, so we've closed the opt-in. """ So, I was apparently too slow and can't test this patch anymore... also, YouTube is crashing in trunk on bug #171336. But disabling/enabling site-specific quirks in MiniBrowser definitely toggled the problem when I tested it earlier today. So let's go with this.
Comment on attachment 308908 [details] Patch Clearing flags on attachment: 308908 Committed r216139: <http://trac.webkit.org/changeset/216139>
All reviewed patches have been landed. Closing bug.