[media] Support DecoderBuffer-based Decode() in DXVAVDA

Also adds support for empty buffer to VTVDA, since this feature is
supported on Windows.

Bug: 522298
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I15fcbee034b4be6c56d04b283931a7c4ea6b82ab
Reviewed-on: https://chromium-review.googlesource.com/1056322
Commit-Queue: Dan Sanders <sandersd@chromium.org>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558422}
3 files changed