GitLab

It is basically a mimic of the h264 picture, and will be used in the
D3D11Vp9accelerator class, when that is ready. There also appear to be
two styles for accelerators to downcast, where vaapi & V4L2 use
as___Picture() methods to get a raw pointer, but D3D11 just uses static
casts. I think a future good cleanup is to get rid of the extra methods
and not rely on forward declarations.

Bug: 881922
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: I6a7cfbb81e230a7ea46ae3c3e27aebf52a559913
Reviewed-on: https://chromium-review.googlesource.com/1213871
Commit-Queue: Ted Meyer <tmathmeyer@chromium.org>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589695}