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<!-- 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
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- [x] These changes do not require tests because geckolib :-(
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r? @bholley
cc @heycam
Source-Repo: https://github.com/servo/servo
Source-Revision: cbf71a2cf39e792f75309e68f7cabe862d4a70eb