The patch in bug 1452786 uses InterfaceHasInstance, not InterfaceIsInstance. The two have pretty similar behavior, so no tests noticed this...
Attachment #8971111 - Flags: review?(kyle) → review+
Pushed by firstname.lastname@example.org: https://hg.mozilla.org/integration/mozilla-inbound/rev/e515ebef17d0 The WebIDL isInstance should be a pure brand check, not an instanceof-like check. r=qdot
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