This is to workaround a Chrome limitation that CDM must be initialized
before starting the playback. CDM can only be initialized with a valid
'pssh'.
Change-Id: Ia34e90dac42abbcdf0193fe4e3c971c87debdd42
Extract encryption related handlings from Fragmenter and move into new
class EncrpytingFragmenter.
Change-Id: Id42493cd321fd7e306f8ce522c7ff04990965256