The system audio can be initiated by Tv itself or by AVR through
<Set System Audio Mode> CEC message.
This CL also includes:
- Add HdmiConstants, HdmiUtil class to handle various constants and
utility functions.
- Add default message dispatcher to all queued actions.
- Add an argument on HdmiControlService.removeAction(class) to prevent
from removing the caller itself.
Change-Id: I9fd9089bed876f04b58c483879b64edfae94a298
63a2e0696c