glwindow webxr backend doesn't work on three.js rollercoaster

[jdm]

godot:~ jdm$ /Volumes/Servo/Servo.app/Contents/MacOS/servo http://rawcdn.githack.com/mrdoob/three.js/r105/examples/webvr_rollercoaster.html --pref dom.webxr.enabled --pref dom.webxr.glwindow
THREE.WebGLRenderer
105
[2019-08-27T21:10:07Z ERROR offscreen_gl_context::draw_buffer] The given GLContext doesn't support requested antialising
THREE.WebGLRenderer: WEBGL_depth_texture extension not supported.
[2019-08-27T21:10:07Z ERROR offscreen_gl_context::draw_buffer] The given GLContext doesn't support requested antialising
[2019-08-27T21:10:07Z ERROR offscreen_gl_context::draw_buffer] The given GLContext doesn't support requested antialising
[2019-08-27T21:10:07Z ERROR offscreen_gl_context::draw_buffer] The given GLContext doesn't support requested antialising
[2019-08-27T21:10:07Z ERROR offscreen_gl_context::draw_buffer] The given GLContext doesn't support requested antialising
[2019-08-27T21:10:09Z ERROR servo::context] Context is not current. Forgot to call prepare_for_composite?
[2019-08-27T21:10:09Z ERROR servo::context] Context is not current. Forgot to call prepare_for_composite?

I get a solid blue screen with no actual webgl content when I press the "Enter XR" button.

[jdm]

The single existing window also no longer responds to pressing escape.

[gterzian]

I get a second window, hidden behind the one showing the blue screen, and I'm guessing you actually do as well. Just move the one with the blue screen to see the second one with the roller coaster.

When you put the other window showing the roller coaster in front, and you press escapre, you get: called Result::unwrap()on anErr value: "SendError(..)" (thread WRRenderBackend#0, at src/libcore/result.rs:1084)

Or sometimes you get the error noted at #23986

[paulrouget]

Also there is an issue where the gl contexts are not made present in the right order.

[jdm]

This indeed works as described in #24073 (comment).