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The code guide doesn't allow "using namespace", and they have
a tendency to cause problems with jumbo builds so this is just
a cleanup to avoid possible future problems.

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;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ibf519c5e4ddb0497961f1befa8de416039e4fc61
Reviewed-on: https://chromium-review.googlesource.com/992318Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#548386}