A frames timing function is a type of timing function that divides the input time into a specified number of intervals of equal length, each of which is associated with an output progress value of increasing value.
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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#15740.
- [X] There are tests for these changes, and web-platform-tests/css-timing-1 also provides tests.
Source-Repo: https://github.com/servo/servo
Source-Revision: 15cf1acc720197b80ff1ad97ea5ddc495f5744fd