better support multi-DRM with one ContentProtection element

[joeyparrish]

Currently, shaka.player.DashVideoSource.ContentProtectionCallback only allows the creation of one DrmSchemeInfo object per ContentProtection element. So although it is possible for a provider to support multiple DRM schemes, the must then use multiple ContentProtection elements as well.

Since ContentProtection can make use of application-specific extensions, there is no reason one ContentProtection element cannot describe, in an app-specific way, multiple DRM schemes. A future refactor of ContentProtection interpretation should take this into account and provide a natural API for generating multiple DrmSchemeInfos.

[joeyparrish]

This could even be needed without app-specific extensions to ContentProtection. For example:

<ContentProtection schemeIdUri="urn:mpeg: dash:mp4protection:2011" value="cenc"/>

For some apps, this should be enough to supply a list of DrmSchemeInfos with license server endpoints for all the various DRM schemes that content provider uses.

[kelvinoliveira]

Added support for multiple DRM schemes per ContentProtection and simplified DRM scheme configuration. #71

Could not find shaka.player.DrmInfo class on version 1.5.0 as stated in https://shaka-player-demo.appspot.com/docs/shaka.player.DashVideoSource.html#ContentProtectionCallback

Maybe, this file is not up to date
https://github.com/google/shaka-player/blob/4cc4e96dbd5d2fd1b47e622eb8505d3ab4848cc0/shaka-player.uncompiled.js

I think that, this line of code should be inserted:
goog.require('shaka.player.DrmInfo');

[tdrews]

The library does not export shaka.player.DrmInfo. Your application should return an array of objects like shaka.player.DrmInfo.Config from your interpretContentProtectionCallback. For example,

return [{
    'keySystem': 'com.widevine.alpha',
    'licenseServerUrl': LICENSE_SERVER_URL,
    'withCredentials': true
  }];

[kelvinoliveira]

Thank you, It's is working now.