This is required to handle the case that an application wants to turn
on/off the caption explicitly (e.g. TvView in PIP). TV input service
implementation must respond to the request immediately to avoid any
legal implication since the captioning is imposed by the law in many
countries.
Bug: 14121898
Change-Id: I9600debae709fdc99065d7a0138ae69d1dffc9ba
2c1c31c7ae