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Removed ArrayBufferViewContents trait and dependent uses.
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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
- [ x ] These changes fix#15551
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- [ x ] These changes do not require tests because it's just unused trait and @jdm said, "No need for automated tests; if the build succeeds, it's good enough for a PR."
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Source-Repo: https://github.com/servo/servo
Source-Revision: 82d05a046d69cef76a4c5106c1ce6adff2aae093