PING: Align exposing scalabilityMode with the WebRTC "hardware capabilities" check

[aboba]

Transferred from w3c/webrtc-svc#92

This issue is being filed as part of the w3cping/privacy-request#117

There have been discussions in other issues around preventing WebRTC-related hardware capabilities from being used for browser fingerprinting. For example

• Expose powerEfficientEncoder/Decoder if MediaCapabilities allows it webrtc-stats#732 (comment)
• The HW exposure check does not solve Cloud Gaming use cases webrtc-stats#730

This issue is to verify that sites would be unable to learn scalabilityMode before the 6.1. Limiting of Hardware Capabilities checks have passed (or if not, that other comparable protections are in place). It might also be ideal to reference the above check in this spec

[aboba]

Note: Issues 730 and 732 have been closed, pending MEDIA WG discussion of whether Media Capabilities should require user permission before returning information on encoder or decoder capabilities.

[chrisn]

Discussed in Media WG meeting 12 December 2023 (minutes). See also #176.