Previews, as seen when this build job started (1696617):
WebGPU _{webgpu.idl | Explainer | Correspondence Reference}
WGSL _{grammar.js | wgsl.lalr.txt}

For the record here's how I'm thinking we can deprecate/remove this from Chromium (taking slight advantage of #4781):

1. • Update validation to match this PR, leaving maxInterStageShaderComponents unused by validation.
     • This should not be a breaking change because it was already necessary to raise maxInterStageShaderVariables to take advantage of it (there might be some VERY particular situation where you could raise maxInterStageShaderComponents without raising maxInterStageShaderVariables but if so it's very unlikely to be used).
   • Change GPUSupportedLimits.maxInterStageShaderComponents (adapter.limits.maxInterStageShaderComponents or device.limits.maxInterStageShaderComponents) to return maxInterStageShaderVariables * 4.
     • This could also technically break something because the device won't expose the same value you requested, but that seems equally unlikely to break anything (except CTS).
     • Now requiredLimits still accepts maxInterStageShaderComponents, but doesn't do anything with it.
   • Deprecate both the GPUSupportedLimits.maxInterStageShaderComponents accessor and requiredLimits.maxInterStageShaderComponents.
2. Watch deprecation telemetry to make sure usage goes down.
3. Remove the limit from GPUSupportedLimits and stop accepting it in requiredLimits.
   • Note that Allow unknown limits to be requested with value undefined #4781 means any sites doing { requiredLimits: { maxInterStageShaderComponents: adapter.limits.maxInterStageShaderComponents } } would actually not break even though they would produce deprecation warnings. We can't detect this robustly.
   • If we don't do that, Chromium can keep a quirk to do that, but only for maxInterStageShaderComponents, as someone suggested in last week's meeting.

(Rebased with no change after landing #4781)