Enable coverage collection when using the test server, which is substantially faster than running in separate, isolated processes.
Use clang's `__llvm_profile_*` APIs to reset the counters between each test case run.
Change-Id: I01f8d0c1b3f215f66cfa50ef0fd51f2522c2ea57
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/113880
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>