Change-Id: I0a3d0e205922bbb4015955e04d51b7a9a4fa86e1
This CL also includes two related changes: 1. Support serialization of raw PSSH box; 2. Refactor segmenter interface a bit. Change-Id: I668aa01a5a5ff524ad6fe74976339a3fd499120a
(second attempt due to conflicts). Change-Id: I2143921bcacdbaa6cfcaf59602713294b4b1f6ee