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This is a potential fix for #12842. I have done only the math to handle simple transforms because it's three AM, but I'd like @pcwalton to verify my approach, or suggest an alternative.
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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 partially fix#12842 (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: 5f169581dc290e3cf0e8d6e7fc0550f1031fb25f
b79bea109c