MediaStream playback through audio and video elements
- [X] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] There are tests for these changes
<!-- 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/23157)
<!-- Reviewable:end -->
Update WebIDL.py
I'm working on getting [attributes on types landed in upstream webidl](https://bugzilla.mozilla.org/show_bug.cgi?id=1359269). In preparation for that, I'd like to update WebIDL.py and deal with all the conflicts first so that updating for that bug is easier.
(This PR doesn't need to be reviewed and landed right now, I can just roll it into the PR for implementing attributes on types, but I suspect it would be easier to land this first)
Probably should squash before landing, the steps are separated out for ease of review.
r? @nox @jdm
<!-- 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/22934)
<!-- Reviewable:end -->
Initial webrtc and getUserMedia DOM support
This is able to reach the point where connections are properly negotiated and ready to exchange streams.
<s>The `toJSON()` stuff doesn't work yet, so most example code will need to be tweaked to manually construct JSON first before sending SDP and ICE messages over websockets. I'll add support for this soon. (This may need webidl tweaks to support `[Default]` and `toJSON()`)</s>
For some reason I haven't yet figured out, connections are one-way, Servo is able to receive streams but the other end doesn't see the streams Servo sends. I don't think this is due to https://github.com/servo/media/issues/191, but that bug is making it harder to test.
This implementation simply drops streams that it receives, without connecting them up to any output elements, since servo-media-player doesn't yet have mediastream support.
Since servo can neither effectively send nor receive streams this implementation isn't useful yet, however it is getting large and I figured I'd get it reviewed and landed early as a base.
r? @jdm
<!-- 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/22780)
<!-- Reviewable:end -->
Update rust-mozjs
These changes adjust our uses of the rust-mozjs APIs to accommodate the changes in https://github.com/servo/rust-mozjs/pull/450.
---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#22342.
- [x] There are tests for these changes
<!-- 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/22353)
<!-- Reviewable:end -->
The following IDLs have the src/href attributes typed as a DOMString
while in the spec the attribute has been updated to be a USVString:
- HTMLIFrameElement
- HTMLImageElement
- HTMLInputElement
- HTMLLinkElement
- HTMLMediaElement
- HTMLScriptElement
