Dawn: refactor texture uploading from GrDawnTexture to GrDawnGpu.

We'll need this for a proper implementation of onUpdateBackendTexture().

Change-Id: I4b9ac93934ef39ed3c82a55f7d74fc1f826f7740
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/323558
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Stephen White <senorblanco@google.com>
4 files changed