Implement XRInputSource, as defined in the WebXR specification

I am going to help this.

OpenVR and Oculus controllers didn't provide targetRaySpace and gripSpace [1] info from their SDK. We only have controller pose that supposes to be grip space, however, it seems like still need a little bit offset to help the grip gesture could be put at the right position. In terms of target ray space, the only way we can do is tuning the position and hard-coded define it internally. It looks like it will happen similar issues like Gamepad API when handling btn and axis mapping in WebVR 1.0. For more wise approach, we should consider to move this information into profiles [2].

[1] https://immersive-web.github.io/webxr/#dom-xrinputsource-targetrayspace
[2] https://github.com/immersive-web/webxr-input-profiles/tree/master/packages/registry/profiles

I will keep working on Gamepad module for XRInputSource at Bug 1617023. I think It is ready to review once Bug 1614496 is landed.

MozReview-Commit-ID: 5pwtTYFawBk

I think it is good enough to review, and I will follow up other related bugs.

Backed out for build bustages.

Push with failure: https://treeherder.mozilla.org/#/jobs?repo=autoland&selectedJob=296698848&resultStatus=testfailed%2Cbusted%2Cexception&revision=717f97c0d8719f0d92b3e5b4563c5c0c0998de09

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=296698848&repo=autoland&lineNumber=37113

Backout: https://hg.mozilla.org/integration/autoland/rev/ab5d839fd72dc77633dc58103df5234ba645b1e0

(In reply to Razvan Maries from comment #9)

Backed out for build bustages.

Push with failure: https://treeherder.mozilla.org/#/jobs?repo=autoland&selectedJob=296698848&resultStatus=testfailed%2Cbusted%2Cexception&revision=717f97c0d8719f0d92b3e5b4563c5c0c0998de09

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=296698848&repo=autoland&lineNumber=37113

Backout: https://hg.mozilla.org/integration/autoland/rev/ab5d839fd72dc77633dc58103df5234ba645b1e0

It works if we land the patch of Bug 1627141 together.

I can move these few lines that cause compiling error to Bug 1627141.

https://hg.mozilla.org/mozilla-central/rev/f1a8a490d36c