Add the support for playready scalable licenses

What steps will reproduce the problem?
     1. Try to play an MPEG-DASH stream with playready scalable license in the CastMediaPlayerStreamingDRM player or a custom receiver.
    (e.g.: http://playready.directtaps.net/media/dash/big_buck_bunny.HD.adap.enc.singleKID.rotleaf10s.dash_ond/big_buck_bunny.HD.adap.dash_ond_720.mpd)
     2. This mpd may not work as itself in the reference player. Please use the underlying mp4 segments with a reference payer compatible mpd in that case.

What is the expected output? What do you see instead?
     PlayReady is supposed to look at the ELS for a leaf license and bind with root license. The root license may be proactively acquired before playback starts. 
     Here are the issues, I’m getting:
    1. I’m able to generate challenge & acquire license for WRMHeader-4.0.0.0 using generateKeyRequest (old EME draft API). But still ELS(from moof->pssh) is NOT binding or playing the content.
    2. InitData with WRMHeader-4.1.0.0 gives ’keyerror’.
    3. requestMediaKeySystemAccess (new EME draft API) gives “Keysystem 'com.microsoft.playready' is not supported” error.

What version of the product are you using? On what operating system?
     Tried with chromecast ver 1.0 and ver 2.0. Sender is ‘Google Cast Sample’ from chrome browser in OS X.

Please provide any additional information below.
     The given MP4 segments from directtaps site, have moov->pssh with WRMHeader with DECRYPTORSETUP=ONDEMAND and moof->pssh with ELS. Usually, the ELS will only contain a leaf license which is chained to a root license.

Original issue reported on code.google.com by vinod....@gmail.com on 11 Oct 2015 at 9:47

ashley1982 / google-cast-sdk

Add the support for playready scalable licenses #661