gpu: Use workarounds to selectively enable CMAA

To get wider testing of the impact of using CMAA for WebGL selectively
enable it by default for "Broadwell GT2" ChromeOS devices.

This was achieved by adding a workaround disabling CMAA on all devices
with an exception for the GPU found in ChromeOS devices like samus.

BUG=535198
TEST=Boot samus device and with added logging observe that CMAA is
activated for WebGL. Use --gpu-testing-device-id/--gpu-testing-vendor-id
to override the device ID and observe "disable_framebuffer_cmaa" listed
under "Driver Bug Workarounds."
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2112513003
Cr-Commit-Position: refs/heads/master@{#402913}
6 files changed