Add some support for WPT tests in an Android emulator through WebDriver
This succeeds on my machine:
`./mach test-wpt --product servodriver --binary etc/run_in_headless_android_emulator.py --binary-arg servo-x86 --binary-arg target/i686-linux-android/release/servo.apk /_mozilla/mozilla/DOMParser.html`
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Refactor run_in_headless_android_emulator.py out of mach test-android-startup
… and make it more careful about not leaving zombie processes behind.
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Support memory report logs with interleaved non-report output
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`line 30-31` in `servo/etc/memory_reports_over_time.py` should just ignore any line that doesn't begin with `|`.
The new if statement added such as `if line.startswith('|'):` then continue to append. So, only lines begin with `|` will be appended.
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- [ ] These changes fix #20257(github issue number if applicable).
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Include non-upstream metadata changes in WPT sync.
The original sync work excluded changes to metadata files under tests/wpt/mozilla under the assumption that any change in test results indicated an existing intermittent issue. This is incorrect, because these tests rely on shared infrastructure with upstream, so the results can be influenced by syncing.
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