Make scroll-snap-{coordinate, destination} discrete animation.
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https://bugzilla.mozilla.org/show_bug.cgi?id=1387941
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Make -moz-appearance animatable
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We convert a perspective function into a ComputedMatrix, but we apply the
perspective length to a wrong matrix item. We should put it into m34,
instead of m43. m43 is for translate parameter Z.
Introduce and derive ComputeSquaredDistance
This new trait merges the former `Animatable` methods `compute_distance` and `compute_squared_distance`.
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Now that we do process normal traversal even in the case of throttled animation
flush so that we don't need to do special handling for the case.
Note about the comment in has_current_styles():
the remaining animation hints is not caused by either this patch or the
previous patch in this patch series, it's been there in the first place, but
it should be fixed somehow later. See bug 1389675.
MozReview-Commit-ID: JojHufxNCiS
Deduplicating code is nice, and it will help us when we make the bit
propagation more complicated in upcoming patches.
MozReview-Commit-ID: KIQnNJVayrM
The buggy animation handling isn't a regression, since currently we pass
UnstyledChildrenOnly in those cases, which blocks the animation traversal
in Servo_TraverseSubtree.
In general I really wanted to handle these two paths together. But there's
enough broken with the NewChildren path that I wanted to scope the buginess
as tightly as possible. And I really need to separate the handling here from
StyleDocument() to make the restyle root stuff work.
MozReview-Commit-ID: 9F0mcQl7AAX
Doing anything else is non-sensical, since we're not guaranteed to reach all of
the bits from traversal Y when doing traversal X.
MozReview-Commit-ID: FQliRxBan70
