This allows a DRM client to open a locally-cached file on behalf of the DRM server so the DRM server no longer requires the sdcard_r permission to access the file's metadata. Specifically, this adds an optional attribute FileDescriptorKey to the DrmInfoRequest. This change is dependent on this Widevine CL: https://widevine-internal-review.googlesource.com/#/c/1330/ Relevant bug reports: bug: 6426185 Change-Id: Ia7bcb2455c7a55fa4c7c7061de4d672957c7ac0a