[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
am: f583da6005

Change-Id: I9002810c0569b91ea6e17c84afaa798c84490fe1