AudioTrack: support ENCODING_IEC61937

Set DIRECT flag.
Use audio_has_proportional_frames() instead of audio_is_linear_pcm()
where appropriate.

Bug: 24541671
Bug: 20891646
Bug: 26373761
Change-Id: Ia32036b18683b084d6c9887593df87397ea0afd9
Signed-off-by: Phil Burk <philburk@google.com>
9 files changed