FrameLayerBuilder requires the the (frame,per-frame-key) for each display item is unique. It only enforces this in certain situations though, so there's cases where we've gotten away without this.
Retained display lists introduces more situations where we rely on this, so I've found a few.
MathML nsDisplayNotation and nsDisplayMathMLBar are the two fixed by this patch.
FrameLayerBuilder requires the the (frame,per-frame-key) for each display item is unique. It only enforces this in certain situations though, so there's cases where we've gotten away without this.
Retained display lists introduces more situations where we rely on this, so I've found a few.
MathML nsDisplayNotation and nsDisplayMathMLBar are the two fixed by this patch.
nsIFrame::mClass is of type enum class nsQueryFrame::ClassID which is
a strict subset of the nsQueryFrame::FrameIID values. For a concrete
frame class, its FrameIID is the same numeric value as its ClassID.
MozReview-Commit-ID: 1N0AkCGo1ol