Rotate animation
Add rotation interpolation code for the case where their direction vectors are equal.
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#11808 (github issue number if applicable).
- [X] There are tests for these changes
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Do not crash on partial calc interpolation
It should always be possible to interpolate between CalcLengthOrPercentage points.
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#12151 (github issue number if applicable).
- [ ] There are tests for these changes (*I STILL NEED TO WRITE TESTS*)
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This commit adds a need_index prop to the style system, and autogenerates
iterators, and a get_xxx_mod(i) function from a get_xxx_prop() and
get_xxx_at(index) functions.
This allows us to (finally!) take rid of the as_servo() hack. There are a few
unimplemented clones, but I'm just too lazy for that right now.
