Implementing class to play tones

+ This class will be used by the DialerRingtoneManager to play the
call waiting tone. It exists to encapsulate the logic to play a tone
in a background thread.
+ The TonePlayer includes some thread safety measures, but is not
meant to be shared between multiple threads

Bug=26936401
Change-Id: I630959177fcd8a4fc8ba7d3153f036746ad8a4cf