Support None and NotSet for the fallback type of SVGPaint.
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We didn't set None and NotSet for the fallback type of SVGPaint, and it caused the fallback color is wrong when fallback color is empty or keyword `none`. So, we add the None and NotSet support for it.
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We need to use enum instead of Either since we can't interpolate stroke-* between
unitless length and unit length(e.g. '5' -> '10px').
This coomit make following:
* Introduce SVGLengthOrPercentageOrNumber on computed and specified values.
* Make SVGLengthOrPercentageOrNumber animatable.
* Make stroke-dasharray not-accumulate.
Make content animatable
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column-count should be greater than or equal to 1. Also it should be less than
or equal to nsStyleColumn_kMaxColumnCount since we limit it in
set_column_count().
Make -moz-appearance animatable
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Move percentage to mod.rs
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The tests in the issue worked for me locally.
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Make list-style-type animatable
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stylo: Bug 1374233 - Clamp interpolated values for properties which need to be restricted
Some properties only accept non-negative values, or values greater than or equal to one. It is possible to produce an negative interpolated values while using negative timing functions, so we have to apply a restriction to these values to avoid getting invalid values.
For example, line-height must be non-negative, but the output progress of some timing functions (e,g. cubic-bezier(0.25, -2, 0.75, 1)) may be a negative value, so the interpolated result of line-height is also negative.
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We already have NonNegativeLength and NonNegativeAu, so we can re-use it
to define the specified value and the computed value of border-spacing.
And then implement ToAnimatedValue for it.
MozReview-Commit-ID: CLckpKMYVXU
