am 8946ab26: A ThreadedSource wraps around an existing MediaSource and reads output buffers on a separate thread. It\'s now used for the vpx decoder to decode frames ahead of time to improve playback performance.

Merge commit '8946ab2618a4eebfdf7b00c6b68e6a5d8432cafa' into gingerbread-plus-aosp

* commit '8946ab2618a4eebfdf7b00c6b68e6a5d8432cafa':
  A ThreadedSource wraps around an existing MediaSource and reads output buffers on a separate thread. It's now used for the vpx decoder to decode frames ahead of time to improve playback performance.