This CL:

1) Move files around to let them make more sense.
browser/net_init_native_callback.cc -> browser/net/init_native_callback.cc
browser/aw_resource.cc -> common/aw_resource.cc

2) Removed aw_metrics_service_client.{h,cc} and
use aw_metrics_service_client_impl.{h,cc} to replace them.

Hitting the same banned function usage:
Use base/task_scheduler/post_task.h instead of the blocking pool.

Hence requires no presubmit check.

NOPRESUBMIT=true
BUG=716604

Review-Url: https://codereview.chromium.org/2886283005
Cr-Commit-Position: refs/heads/master@{#473299}