Merge "Add uptimeNanos to SystemClock" am: 52c8422ea1 am: c7a2225665 am: ba7efc63cc

Original change: https://android-review.googlesource.com/c/platform/system/core/+/1394287

Change-Id: Ib9e04266b47bdc6129c10c72ee35222c49beff1e