media/gpu/test: Add new VDA test for multiple queued buffer decode requests.

This CL adds a test that requests multiple bitstream buffer decodes, without
waiting for the result of the previous decode operation.

TEST=ran new VDA tests on nocturne

BUG=879065

Change-Id: I72352206ae56e9a3e4f62f87271c978bbad7bfee
Reviewed-on: https://chromium-review.googlesource.com/c/1419560
Commit-Queue: David Staessens <dstaessens@chromium.org>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624723}
5 files changed