Viewer: enable Dawn/D3D11 and Dawn/D3D12 backends

Change-Id: I84a394e4b5a7921c3d09cc1dfe151ff124213bbf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1087857
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
Reviewed-by: Kaylee Lubick <kjlubick@google.com>
7 files changed