[automerger] [DO NOT MERGE] Update Platform Security String to 2019-03-01 for nyc-dev Bug:122541777 am: 7a403979d6 am: e56e5efec9 am: 87877d530a am: 33ecfffc1f skipped: 440db90921
am: ed56062889

Change-Id: Ia7158b31b505312b079622e95394ca0cf9f56e99