This CL removes some forward declarations which are no longer needed
and adds one missing declaration which was pulled in from other headers.
These were found by the clang-tidy bugprone-forward-declaration-namespace
check.
Bug: dawn:1414
Change-Id: I8906861e472f2d64a1547c8c6de348cd4151ffb5
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/91742
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>