GLSLstd450SAbs expects a *signed* integer.
abs() of an unsigned number is now a no-op.
Fixes WebGPU CTS tests:
webgpu:shader,execution,robust_access_vertex:vertex_buffer_access:*
Bug: tint:1194
Change-Id: I65c5e9f2f03aac0b788b9ba88c383cbec136d7c6
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/65620
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Kokoro: Ben Clayton <bclayton@chromium.org>
Reviewed-by: David Neto <dneto@google.com>