What is the issue with the HTML Standard?

Now that canvases can be more than sRGB, and can even be floating-point, there is a need to indicate how those pixels are to be tone mapped. This problem has existed for a while in WebGPU, so the proposal (linked below) is just to move WebGPU's solution into the HTML specification, and then point WebGPU at that.

https://github.com/ccameron-chromium/ColorWeb-CG/blob/master/canvas2d_tone_map.md

Of note is that this proposal does not include any non-trivial tone mapping algorithms (it only provides the two trivial ones). The large "future work" section indicates where standardization is going on for that work.