This is on top of https://github.com/servo/servo/pull/15928.
Now that cascade() gets a Device ref, we can use the default computed values
from there to avoid propagating that state all over the place.
Source-Repo: https://github.com/servo/servo
Source-Revision: 8c8edb8731dc01d254839d0922590fba72f278c6
Fixes https://github.com/servo/servo/issues/15207
Refactored as per https://github.com/servo/servo/issues/15207#issuecomment-275171590 .
<!-- Please describe your changes on the following line: -->
- [x] Correct refactor? I'd appreciate any feedback on this.
- [x] ~~~proper borderstyle value for `outline-style: auto;`?~~~ ~~~(EDIT: deferred to a `FIXME`)~~~ (EDIT2: it is now solid for behaviour parity with firefox)
- [x] squash pending PR review
- [x] mako code review
---
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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#15207 (github issue number if applicable).
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- [x] There are tests for these changes
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Source-Repo: https://github.com/servo/servo
Source-Revision: 368af6f8619804244a7d8ba4614f0b4950cfd9f1
