graphite: add slice in DawnTextureInfo and DawnTextureSpec

Chrome may wrap a slice of texture array into a graphite texture
for using textures from d3d11 video decoder, so add slice field
in DawnTextureInfo and DawnTextureSpec

Bug: chromium:335564847
Change-Id: I054ca7ff36b9813ba566827ebbb9153c791d4742
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/844277
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Auto-Submit: Peng Huang <penghuang@chromium.org>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
4 files changed