Currently, non-immersive VR sessions on desktop return the pose of the external HMD. This is unexpected for users, inconsistent with mobile ( issue 695937 ), and prevents use of orientation sensors on desktop (i.e., issue 820308). It also causes the VR runtime to be loaded before the user has an intent to use a headset.

Ideally, we'd immediately switch to using orientation sensors for VR magic window poses on desktop, but there are platform-specific issues (issue 820308, issue 773829). Thus, we should at least stop using HMD poses for now. We can also change the code to use orientation device for magic window on ALL platforms and just have that fail on platforms where there are issues.

We may need to change to report no support for non-immersive sessions. For WebXR, we could go ahead and implement the proposed poseless sessions (Uniform Rendering Path). That is the direction the spec is headed, though the API shape will change. WebVR assumes poses outside presentation if presentation is possible. Thus, we may just need to report a fixed pose, which is similar to Uniform Rendering Path.