TIF: Make TvTrackInfo methods more explicit.

This change addresses the following API council feedback:

TvTrackInfo:
-- Remove all KEY_/VALUE_ constants, and replace with explicit,
   strongly-typed accessor methods.
-- Add additional Bundle getExtras() method (in addition to the explicit
   types); most of the time this Bundle will be null.

Bug: 16542165
Change-Id: Ie48cb170b2bbf07d9460fdc8ed77d7db01799772