detectedPlanes
XRFrame is extended to contain detectedPlanes attribute which contains all planes that are still tracked in the frame.
The set is initially empty and will be populated by the update planes algorithm. If this attribute is accessed when the frame is not active, the user agent MUST throw InvalidStateError.
See also
https
://immersive-web.github.io/real-world-geometry/plane-detection.html#plane-set