Merge "Using Proguard to shrink apk size." into nyc-dev
am: 90e74a5

* commit '90e74a539d92a59da8ea2994c91bac908e4ac7d4':
  Using Proguard to shrink apk size.

Change-Id: Ib124e8aa4e5534bf18e528ec6aed93529f91e2ec