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 <[email protected]>
Reviewed-by: Avi Drissman <[email protected]>
Reviewed-by: Kenneth Russell <[email protected]>
Cr-Commit-Position: refs/heads/master@{#622252}
diff --git a/docs/gpu/debugging_gpu_related_code.md b/docs/gpu/debugging_gpu_related_code.md
index 2739ab3..27f3c2ce 100644
--- a/docs/gpu/debugging_gpu_related_code.md
+++ b/docs/gpu/debugging_gpu_related_code.md
@@ -136,7 +136,14 @@
 
 ### `--enable-gpu-service-logging`
 
-In a debug build, this will print all actual calls into the GL driver.
+In a debug build or a release build with dcheck_always_on=true in GN argument,
+this will print all actual calls into the GL driver.
+
+To use it in Release builds without dcheck_always_on = true, specify GN argument
+enable_gpu_service_logging=true.
+
+For non-rooted devices running production builds, we can not set the command
+line flags. Use about://flags 'Enable gpu service logging' instead.
 
 ```
 [5497:5497:1219/142413:ERROR:gles2_cmd_decoder.cc(3301)] [.WebGLRenderingContext]cmd: kEnableVertexAttribArray