Alternate fix for fragment input deductions in max_variables_count,input

[kainino0x]

I took Erich's test fix #4546, then tried to tweak the original structure of the test so it's clear by construction that it actually tests what it's supposed to test.

Issue: #4538

See also #4539.

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Requirements for PR author:

• All missing test coverage is tracked with "TODO" or .unimplemented().
• New helpers are /** documented */ and new helper files are found in helper_index.txt.
• Test behaves as expected in a WebGPU implementation. (If not passing, explain above.)
• Test have be tested with compatibility mode validation enabled and behave as expected. (If not passing, explain above.)

Requirements for reviewer sign-off:

• Tests are properly located.
• Test descriptions are accurate and complete.
• Tests provide complete coverage (including validation control cases). Missing coverage MUST be covered by TODOs.
• Tests avoid over-parameterization (see case count report).

When landing this PR, be sure to make any necessary issue status updates.

[github-actions]

Results for build job (at dee62c8):

-webgpu:api,validation,render_pipeline,inter_stage:max_variables_count,input:* - 8 cases, 8 subcases (~1/case)
+webgpu:api,validation,render_pipeline,inter_stage:max_variables_count,input:* - 6 cases, 12 subcases (~2/case)
-TOTAL: 284500 cases, 2342678 subcases
+TOTAL: 284498 cases, 2342682 subcases

[greggman]

DOH! Sorry, I missed that there was already a PR up for this. Choose which ever one you prefer.

@ErichDonGubler

[kainino0x]

@greggman The duplicates are #4541 and #4554 for capability_checks,limits. This one and its ancestor #4546 are for a separate test render_pipeline,inter_stage

[greggman]

#4554 includes this as well, and includes the extensions. I can discard it, I can split it (it's updating 2 files), or you can review that. Even if this one is merged we will need the changes from #4554 afterwards for the new builtins.

[kainino0x]

Oh sorry, missed that that PR had two files!

[kainino0x]

Pulled in the extra optional-feature builtins from #4554

[greggman]

I removed the changes to inter_stage.spec.ts from #4554

[greggman]

actually, you'll need to add the enabled stuff to the WGSL or these will fail. Here's my previous PR for reference

[kainino0x]

actually, you'll need to add the enabled stuff to the WGSL or these will fail. Here's my previous PR for reference

Ahh whoops, thank you for catching that! Totally forgot to copy that over. (I didn't test against fixed chromium, I probably should. Seems like the fix will be in Canary very soon so I'll just wait until then and verify this.)