Thumbs up to adding more tests to the GPU bots.

If these tests can be added to an existing test target that would be great; otherwise adding a new target is fine.

Note that a couple of the test suites (gpu_unittests, content_unittests) have been found to kill some of the physical bots, perhaps because they try to shut down the X server:
https://cs.chromium.org/chromium/src/content/test/gpu/generate_buildbot_json.py?q=generate_buildbot_&sq=package:chromium&l=1593

Need to be careful to avoid assuming anything about the machine in these new tests, i.e., that it's running xvfb.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e43ad9814b8a1eda2416af7b73e15b44ad0ff400

commit e43ad9814b8a1eda2416af7b73e15b44ad0ff400
Author: Emircan Uysaler <emircan@chromium.org>
Date: Thu Apr 05 22:32:09 2018

Detect H264 slices of the same frame in VEAUnittest

This CL is based on https://codereview.chromium.org/2538883002/.

This CL adds checks similar to H264Decoder::IsNewPrimaryCodedPicture() to
determine if the given H264 slice belongs to a new frame. On Mac and Win,
we can have multiple slices per frame and this causes problems.

Bug:  669678 , 828176
Test: Tested VEAUnittest on MBP 2016.
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;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I4781bacd199ae0545a3f46b37765b126f947b92e
Reviewed-on: https://chromium-review.googlesource.com/991198
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Emircan Uysaler <emircan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548590}
[modify] https://crrev.com/e43ad9814b8a1eda2416af7b73e15b44ad0ff400/media/gpu/h264_decoder.cc
[modify] https://crrev.com/e43ad9814b8a1eda2416af7b73e15b44ad0ff400/media/gpu/h264_decoder.h
[modify] https://crrev.com/e43ad9814b8a1eda2416af7b73e15b44ad0ff400/media/gpu/video_encode_accelerator_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fe4e0d4b82813da20a8be333719f22c7c6c1c9ca

commit fe4e0d4b82813da20a8be333719f22c7c6c1c9ca
Author: Emircan Uysaler <emircan@chromium.org>
Date: Tue Apr 24 17:35:09 2018

Tweak video_encode_accelerator_unittest to use base::Test

This CL is similar to https://codereview.chromium.org/2521793002. In order to
run this test on bots, we use base::LaunchUnitTestsSerially as a test runner.

Bug: 828176
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
Change-Id: I49f6331f04168b998edf5504a5c9b39c31e78784
Reviewed-on: https://chromium-review.googlesource.com/1023112
Commit-Queue: Emircan Uysaler <emircan@chromium.org>
Reviewed-by: Emircan Uysaler <emircan@chromium.org>
Reviewed-by: Kuang-che Wu <kcwu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553194}
[modify] https://crrev.com/fe4e0d4b82813da20a8be333719f22c7c6c1c9ca/media/gpu/BUILD.gn
[modify] https://crrev.com/fe4e0d4b82813da20a8be333719f22c7c6c1c9ca/media/gpu/video_encode_accelerator_unittest.cc