WPT details: WebGPU/WGSL have a conformance test suite (https://github.com/gpuweb/cts) that is regularly pulled into Chromium and part of the testing of Dawn/Tint in Chromium.
The WebGPU maxBindGroupsPlusVertexBuffers limit is the maximum number of bind group and vertex buffer slots used simultaneously, counting any empty slots below the highest index. It is validated in createRenderPipeline() and in draw calls. This change adds maxBindGroupsPlusVertexBuffers to the GPUSupportedLimits interface, and as an accepted key by the GPUDeviceDescriptor.requiredLimits record.