Format component size_of_test
<!-- Please describe your changes on the following line: -->
Format `components/size_of_test` by:
```
rustfmt components/size_of_test/*.rs
```
---
<!-- 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
- [ ] These changes fix part of #21373.
- [x] These changes do not require tests because they format code only.
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<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21661)
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chansuke commentedSep 10, 2018
•
edited by jdm
Format
components/size_of_testby:./mach build -ddoes not report any errors./mach test-tidydoes not report any errorsThis change is