Chrome Version: Chrome 70.0.3538.64
OS: Android 9, Pixel 1

When creating an AR session with `environmentIntegration: true` and `outputContext: <XRPresentationContext>`, the request is rejected with: `DOMException: The specified session configuration is not supported`.

This is reproducible in the codelab[0] as well as Chacmool[1] page. There has not been any changes to these codebases since the summer, and there's been no platform API changes AFAIK.

[0] https://googlecodelabs.github.io/ar-with-webxr/final/
[1] https://web-education-ar-demo.appspot.com/

What steps will reproduce the problem?
(1) Go to an AR page above, request session, see error.


What is the expected result?

To start an AR session.

What happens instead?

The request is rejected.