Merge "C2SoftMp3Dec: Treat timestamps as signed values" into sc-dev am: 8d043d8c am: 99fafb71 am: f04785bc

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/15340733

Change-Id: I8a2dfa3e94f4073493dba2ab796978182a4759a8