This reverts commit 9f1eb0ba.

Reason for revert: speculative revert due to cc_unittests failures
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20Tests%20%28dbg%29%281%29%2832%29/51119

Original change's description:
> Switching all ui/gl dependent tests to SwiftShader
> 
> This cl's switches cc_unittests and viz_unittests from OSMesa
> to SwiftShader and fixes other issues related to that change.
> 
> Bug chromium:848035
> 
> 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;master.tryserver.blink:linux_trusty_blink_rel
> Change-Id: Ib1b58e02d4df4a687ef7be57284c06097bdeca94
> Reviewed-on: https://chromium-review.googlesource.com/1070490
> Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
> Reviewed-by: danakj <danakj@chromium.org>
> Reviewed-by: Antoine Labour <piman@chromium.org>
> Reviewed-by: Eric Karl <ericrk@chromium.org>
> Commit-Queue: Alexis Hétu <sugoi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#572442}

TBR=danakj@chromium.org,sugoi@chromium.org,dcastagna@chromium.org,piman@chromium.org,ericrk@chromium.org

Change-Id: I5957fd458b172fd58d4d1fe866e4b07be600c6cb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
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;master.tryserver.blink:linux_trusty_blink_rel
Reviewed-on: https://chromium-review.googlesource.com/1125599Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572485}