Merge "[BUG] AudioService: PlaybackActivityMonitor: fix exploding list" am: 3e5cf8398a am: d2648ea1d7 am: f130b84f71 am: ef3cafc9e1

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1421470

Change-Id: Ia34fb2bb8817d63955da4bf5920a8834093850ff