Steps to Reproduce: 1. Load http://www.seriouseats.com/recipes/2017/08/roasted-carrots-black-sesame-dressing-recipe.html in a ToT debug build. Expected: Carrots. Actual: Crash. For me, every time. I have r221082. ASSERTION FAILED: !m_valueOrException /Users/thorton/src/WebKit/OpenSource/Source/WebCore/bindings/js/DOMPromiseProxy.h(291) : void WebCore::DOMPromiseProxyWithResolveCallback<WebCore::IDLInterface<WebCore::FontFaceSet> >::resolve(typename IDLType::ParameterType) [IDLType = WebCore::IDLInterface<WebCore::FontFaceSet>] 1 0x195c0a9ad WTFCrash 2 0x188aab579 WebCore::DOMPromiseProxyWithResolveCallback<WebCore::IDLInterface<WebCore::FontFaceSet> >::resolve(WebCore::FontFaceSet&) 3 0x188aac779 WebCore::FontFaceSet::completedLoading() 4 0x18856f1b0 WebCore::CSSFontFaceSet::decrementActiveCount() 5 0x188574363 WebCore::CSSFontFaceSet::fontStateChanged(WebCore::CSSFontFace&, WebCore::CSSFontFace::Status, WebCore::CSSFontFace::Status) 6 0x18856d5c7 WebCore::CSSFontFace::setStatus(WebCore::CSSFontFace::Status)::$_14::operator()(WebCore::CSSFontFace::Client&) const
*** This bug has been marked as a duplicate of bug 176525 ***
Turns out this isn't a duplicate.
Upon closer investigation, 176525 fixed it but I'd still like to add a test and update the patch with a slight style change.
Created attachment 320581 [details] Patch
Comment on attachment 320581 [details] Patch Clearing flags on attachment: 320581 Committed r221948: <http://trac.webkit.org/changeset/221948>
All reviewed patches have been landed. Closing bug.
<rdar://problem/34694033>