Description:
Add the a policy to set a device hostname on a Chrome device in the Active Directory admx templates. 

Use case:
Customers would like the ability to set the hostname of a Chrome device through policy in order to identify the device on the network. This is currently supported on the device (http://crbug/676195), and there is a test on the Chrome cloud-managed side (http://b/72481557). In order for ChromeAD customer to take advantage a policy needs to be added to the ChromeOS admx templates. 

The client side values can be set as follows: 

Policy=xxx                         xxx
Policy=${ASSET_ID}                 Device's asset ID [1]
Policy=${SERIAL_NUM}               Device's serial number
Policy=${MAC_ADDR}                 Device's MAC address
Policy=xxx+VAR+xxx                 xxx+VAR_VALUE+xxx

In ChromeAD it would be most valuable to allow the AD machine name ${MACHINE_NAME} to be used as a value in addition to or instead of ASSET_ID. Machine name is the way printers can be named in ChromeAD via policy.


Motivation:
This feature would allow customers to identify individual devices on the network for integration into their other enterprise systems. The only way to identify the devices today is with IP address which is subject to change.

Existing workarounds:
None