Update dawn.h -> webgpu.h, dawn_cpp.h -> webgpu_cpp.h.

Also fix some compile breakages from recent Skia changes.
No changes to Skia API.

Change-Id: Ifd0b1d89fb4ea3cf1f6a7170f2f74614276364ae
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257877
Commit-Queue: Stephen White <senorblanco@chromium.org>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
22 files changed