Display property animation for SMIL
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https://bugzilla.mozilla.org/show_bug.cgi?id=1385089
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When display style is changed from 'none' to other in animation-only restyle
we need to resolve descendant elements' style that were in the display:none
subtree.
Three possible ways to resolve the descendant elements' style;
1) Traversing unstyled elements in animation-only restyle
We can't simply traverse unstyled elements in the animation-only restyle
since when we decided to traverse the unstyled elements we don't know yet
the elements will be initially styled or are in display:none subtree. It
will result that the new elements are styled in animation-only restyle,
it's undesirable.
2) Creating a SequentialTask and resolve the descendants' style with
ServoStyleSet::StyleNewSubtree()
We can't resolve the descendants' styles with ServoStyleSet::StyleNewSubtree()
in SequentialTask since at the moment we are still in servo traversal (i.e.
sInServoTraversal is true). That means AutoSetInServoTraversal fails
in PrepareAndTraverseSubtree().
3) Creating a SequentialTask and set restyle subtree hint and defer descendants'
restyle in a subsequent normal traversal
Note that, when we process throttled animations flush, we don't process
normal traversal so the descendants will not be traversed until normal
restyle happens but it will not be a big problem since it's really rare
that user clicks display animation element just at the right moment when
display property changes from none to other. Also, if it will be really
a problem, we should process *only* transform animations on the compositor,
it's ideally right thing to do. Display property never runs on the
compositor.
This patch takes the third approach.
Make grid-template-areas/columns/rows animatable
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Currently, attempting to parse an at-rule that is out of place, such as
an @import rule after a regular style rule, will cause the parser state
to be set to Invalid. This will cause any following at-rule to be
rejected until we encounter a regular style rule, at which point we'll
go back to the Body state. There's nothing in the CSS specs about
needing to reject all following at-rules (or, as the comment above
Invalid says, ignoring the entire rest of the style sheet).
stylo: Implement ToCss for SpecifiedOperation::{InterpolateMatrix|AccumulateMatrix}.
DevTools may serialize an InterpolateMatrix or AccumulateMatrix by
KeyframeEffectReadOnly::GetProperties() (from Gecko side), so we have to implement both.
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- [X] These changes do not require tests because only Chrome-Only API needs this, and the serialization of InterpolateMatrix and AccumulateMatrix are not in the spec.
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Implement ::first-line support in stylo
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Fixes Gecko bug 1324619.
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style: Remove now-unused empty Variables struct.
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The `Servo_GetEmptyVariables` FFI function no longer has any callers from Gecko, so we can remove it and the code that creates/frees that struct.
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