WebXR, WCG and HDR

[svgeesus]

Originally raised in TAG review of Lab

[svgeesus]

WebXR does not directly define the colorspace used, but does require that rendering be to an HTML canvas which implicitly defines what colorspace is used (8bit sRGB).

• Add a color space as an optional feature for requestSession?
• Are 8-bit outputs sRGB encoded?

I notice some confusion between the input colorspace, the output colorspace, and the texture format.

[palemieux]

Propose to close since, as noted above, WebXR relies on canvas and canvas is already discussed in the report.