This was a legacy flag for WinXP which would lose context often during
regular activities (like locking the screen).

R=piman@chromium.org
TBR=kenrb@chromium.org
BUG=606056
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2261893003
Cr-Commit-Position: refs/heads/master@{#413566}