Support src/dst file descriptors for transcoding sessions

The transcoding APIs already accept source and destination
ParcelFileDescriptors and will use them in favour of the source and
destination URIs (which are really file:// URIs now).

This should avoid unnecessary binder calls to open the fds and should
also fix some potential race conditions where the files are deleted
before the URIs are opened

Bug: 183388518
Test: atest TranscodeTest
Change-Id: Idff2a3e97ff316fc301a6eefbcf60396a317da52
1 file changed