[deno] Requested limits are not clamped at the WebGPU defaults

[andyleiserson]

WebGPU specifies a default value for each of the limits it defines. Requesting a limit value smaller than the default is not supported and should be substituted with the default. https://www.w3.org/TR/webgpu/#supported-limits

This is done in Firefox C++ code. It is not currently done by Deno, resulting in failure of the webgpu:api,validation,capability_checks,limits,maxBindGroups:setBindGroup,at_over:limitTest="underDefault";* CTS tests (and presumably also the equivalent tests for other limits).

[sagudev]

I suggest adding Limits::max(Limits), then we could use provided_limits.max(Limits::default()) in implementations.

[Vecvec]

I suggest adding Limits::max(Limits), then we could use provided_limits.max(Limits::default()) in implementations.

I think that this would be useful to be exposed to users if it's added, I've wanted this a couple of times, and manually implemented a cut down version in some of my programs. Personally I think Limits::best_of would be less confusing as alignment limits would go down, not up.

[sagudev]

Personally I think Limits::best_of would be less confusing as alignment limits would go down, not up.

Ah, I forgot about alignment limits.

[sagudev]

Relevant code in servo: https://github.com/servo/servo/blob/f24f225db8b234c0545c57e80356af84e42bcb4b/components/script/dom/webgpu/gpusupportedlimits.rs#L202

[andyleiserson]

At the risk of being unnecessarily verbose, I implemented this with a method called or_better_values_from and added the change to existing PR #8085.