These were helpers to avoid the need for users of implementation-based
swapchains to implement them themselves. They are no longer used and can
be removed.
Also removes SwapChainuUtils.h that's no longer used.
Bug: dawn:269
Change-Id: I3c563edaf107e9ce04f708e8bacae9d231b0f40d
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/126421
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Loko Kung <lokokung@google.com>
961f7eae70