stylo: support all overflow values
overflow:clip doesn't exist, it's just called clip internally. Renamed, and added the other missing values.
I also removed the overflow newtype -- no need for extra code bloat, and it's not protecting us from much.
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/16597)
<!-- Reviewable:end -->
In Gecko, we use double pointers to nsBorderColors to store -moz-border-*-colors.
We can simplify the implementation of computed value in Servo by using Option<Vec>.
As to passing computed values from Servo to Gecko, we might need to use some
binding functions (pre-added in the same Gecko bug, see Bug 1348173).
Note that we added -moz-border-*-colors as sub_properties of the 'border'
shorthand, so we can make the 'border' shorthand reset -moz-border-*-colors
(See Gecko Bug 482692). However, since they are Gecko only non-standard properties,
we should skip these sub_properties while doing unit testing in Servo. The test part
should be convered by Stylo/Gecko already.
A bit refactoring of replacing all ["top", "right", "bottom", "left"] with PHYSICAL_SIDES
is included in this patch, since we've already had PHYSICAL_SIDES for a while.
Introduce intermediate rgba
<!-- Please describe your changes on the following line: -->
This is a PR for https://bugzilla.mozilla.org/show_bug.cgi?id=1356941
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
<!-- Either: -->
- [X] These changes do not require tests because it's for stylo.
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/16587)
<!-- Reviewable:end -->
Add calc method for CalcLengthOrPercentage
* Add calc method to calculate formula value with parent size
* Add unit test case
<!-- Please describe your changes on the following line: -->
Please see this issue: https://github.com/servo/servo/issues/15986
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#15986 (github issue number if applicable).
<!-- Either: -->
- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/16541)
<!-- Reviewable:end -->
This macro will be used for implementation of intermediate type shadows
as well. In the case of intermediate types transparent_color will be
IntermediateRGB::transparent().
