Add enable_gpu_service_logging GN argument and about flag.

1. Add enable_gpu_service_logging GN argument. This can be used in
Release builds without dcheck_always_on=true, and allows the
--enable-gpu-service-logging command line argument to work.

2. Add about flag 'Enable gpu service logging' to let non-rooted
devices enable the --enable-gpu-service-logging flag.

Bug: 839769
Change-Id: Ic6fe4d97aaa6deb51b1f4d30ac4e7aeeaf8b4700
Reviewed-on: https://chromium-review.googlesource.com/c/1401616
Commit-Queue: vikas soni <vikassoni@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622252}
8 files changed