This is a dependency of the WebXR implementation.
In order to support WebXR's navigator.xr.IsSessionSupported call without
displaying any permission dialogue, it is necessary to have a safe way to
detect the capability of running a VR or AR session without activating XR
runtimes or powering on hardware.
API's such as OpenVR make no guarantee that hardware and software won't be
left activated after enumerating devices, so each backend in gfx/vr/service
must allow for more granular detection of capabilities.
By passing true to bDetectRuntimesOnly, the initialization exits early
after reporting the presence of XR runtime software. The Initialize method
will only enumerate hardware and possibly return true when
aDetectRuntimesOnly is false.
Differential Revision: https://phabricator.services.mozilla.com/D54234
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extra : moz-landing-system : lando
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