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Fix interface exposure per [the specs](https://html.spec.whatwg.org/multipage/scripting.html#2dcontext).
One lingering question I have is if [`CanvasPath`](https://html.spec.whatwg.org/multipage/scripting.html#canvaspath) needs to be added to `interfaces.worker.js` since it *is* exposed to the `Worker` environment. I tried adding it to the `interfaces.worker.js` list but it failed tests at https://github.com/servo/servo/blob/master/tests/wpt/mozilla/tests/mozilla/interfaces.js#L82
---
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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 contain a partial fix for #12415 (github issue number if applicable).
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Source-Repo: https://github.com/servo/servo
Source-Revision: 97bcd97ebd7705df8d4d141d18e79073f71b2ba2
This might be a bad idea, especially on the webidl side. However, we started talking about the idea that modelines are a lint error (https://github.com/servo/servo/issues/10719), and these changes would be required before enabling a modeline lint.
If it bitrots, it's easy to recreate with
```
find * -type f -exec sed '/- Mode:/d' -i {} +
find * -type f -exec sed '/ vim:/d' -i {} +
git checkout -- python/tidy/servo_tidy/tidy.py
git checkout -- python/tidy/servo_tidy_tests/spec.webidl
git commit -a
```
Source-Repo: https://github.com/servo/servo
Source-Revision: dff217c2e3ff0b77eeebf62d36c2bf57c044cf14
