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This is a reland of 9f1eb0ba

The only change from the original cl is in cc/test/layer_tree_test.cc,
so TBRing reviewers who approved other parts of this cl.
TBR=dcastagna@chromium.org,piman@chromium.org,ericrk@chromium.org

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}

Change-Id: I85f723ed8a8f7d981a9652cd7979c54d0f1248ae
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/1125899
Commit-Queue: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572623}