Dawn: remove access to deprecated fields in BufferCopyView.

Change-Id: I258565e7652365993671281f4cc196e613483806
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/310062
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Stephen White <senorblanco@google.com>
2 files changed