Add parsing/serialization for grid-{row,column} and grid-area
With this, almost all the grid properties will have been covered in Stylo. I now realize that we have only two more shorthands left to go - `grid` and `grid-template` (both require #16067)
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Correct serialization for border-radius property.
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I don't think there is a way to avoid the clones, or is there one?
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If there is any longhand consisting of both keyword and position, we
should attach both keyword and position for both longhands when serialize
them.
1. To generate a serialized result with keyword, we add a macro function
`to_css_with_keyword` accepted HorizontalPosition and VerticalPosition as
the parameter to finish that. For the longhands which missing keyword, we
use the default keyword.
(`left` for `*-position-x` and `top` for `*-position-y`)
2. Update `Position::to_css` to generate the valid format by calling
`to_css_with_keyword` with HorizontalPosition and VerticalPosition.
3. Update `to_css` to use new `Position::to_css` in background,
background-position, mask and mask-position.
MozReview-Commit-ID: 5Bnhdsi5yeM
Fix -moz-outline-radius shorthand serialization
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These changes aim to solve #15169 correcting the `ToCss` implementation for `LonghandsToSerialize` for the `border-radius` shorthands. They also reduce redundant values like `1px 2px 1px 2px` to `1px 2px` to either sides of the slash.
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Font variant shorthand
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This is a PR of https://bugzilla.mozilla.org/show_bug.cgi?id=1354876
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Cleanup basic shape code
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I began with isolating serialization stuff for `BorderRadius` to help #16340 and #16352, but ended up cleaning a lot of code in `basic_shape.rs` (it's just a cleanup, should be easy to review)
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Limit traversal statistics dumps to subtrees of 50 or more elements and add more values.
On Gecko, we get tons of console spam from 1-element traversals if we don't do this.
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