Merge "Add @Nullable annotations to Task fields" into sc-v2-dev am: 2d7f52505e am: 1572daff43

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16241227

Change-Id: I3cc8545a53796879e7b9dc649f5a1306bb1c6545