v4l2_vea: Fix timestamp of BitstreamMetadata.

Time::FromTimeVal() method will add the offset of UNIX epoch,
and breaks the timestamp check at video_encode_accelerator_unittest.
This CL change it to Time::FromMicroseconds().

BUG=chromium:853185
TEST=pass video_encode_accelerator_unittest at Kevin device

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: Ia13027141062015f904be74b9323a988697fea3a
Reviewed-on: https://chromium-review.googlesource.com/1133612
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575537}
1 file changed