media/gpu/VEA unittest: Test DMABuf-backed input buffers

This adds the command line option, --natvie_input, that VEA unittest passes
DMABuf-backed video frame to VEA.
DMABufs are obtained by gbm though NativePixmap. To create NativePixmap on
Chrome OS, it needs to set up Ozone environment properly. Therefore, this change
also makes VEA unittest dependent on Ozone.

BUG=chromium:895230
TEST=VEA unittest on eve w/wo --native_input

Change-Id: I67526a1b6b6cf1ae74a96000ec2af14995dbd4fc
Reviewed-on: https://chromium-review.googlesource.com/c/1295636
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606788}
13 files changed