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This is a very small set of machines, which have been exhibiting
- rendering artifacts when GPU compositing is enabled
- severe rendering artifacts when GPU raster is enabled

Bug: 875891
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: Ie49a9111b9723977a2b8758f824bba7843238d32
Reviewed-on: https://chromium-review.googlesource.com/1220180Reviewed-by: ccameron <ccameron@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590516}