This CL adds NonNull annotations to a large number of method returns and parameters as part of API council feedback. Bug: 72473424 Test: compilation (docstring-only change) Merged-In: I2f865dde56fe12116c461ad98e9460bf1802ce18 Change-Id: I2f865dde56fe12116c461ad98e9460bf1802ce18 (cherry picked from commit 8fd26f67fdfdedb535ddb8c7d5ededa5dcba40f8)