Wrap FrameDistributor in a thread safe accessor.

Wrap FrameDistributo in a thread safe accessor and make the instance to
accessor a final field in CaptureModule. This should help in avoiding
null checks and NPEs.

BUG: 18414956

Change-Id: I8d25c5a2923a7382f98c523e88f7547f16217a6f
3 files changed