Running "gn check out/GN //media/cast/*" currently reports 127 violations. As part of  issue 599578  we're trying to fix these errors so that //media is clean. Opening this bug to track cleaning up the media/cast directory.

First couple of errors:
ERROR at //media/cast/cast_config.h:18:11: Include not allowed.
ERROR at //media/cast/cast_sender_impl.cc:7:11: Can't include this header from here.
ERROR at //media/cast/cast_sender_impl.h:9:11: Can't include this header from here.
ERROR at //media/cast/cast_receiver.h:13:11: Can't include this header from here.
ERROR at //media/cast/cast_sender.h:15:11: Can't include this header from here.
ERROR at //media/cast/common/transport_encryption_handler.cc:12:11: Include not allowed.

Typical error indicates what is missing:
ERROR at //media/cast/cast_config.h:18:11: Include not allowed.
#include "media/cast/net/cast_transport_config.h"
          ^-------------------------------------
It is not in any dependency of
  //media/cast:common
The include file is in the target(s):
  //media/cast:net
which should somehow be reachable.

Most of these are probably resolved by setting deps variable appropriately in the BUILD.gn file.