[automerger] String16: remove integer overflows am: d0648d8d am: 9de539d0...

[automerger] String16: remove integer overflows am: d0648d8d am: 9de539d0 am: 726007ed am: 4ca82d1d am: 35629db6 am: dc2153c9 am: f479f906 am: e9df4d52 am: dd95a7f1 am: f546acd3  -s ours am: 9ce034ce  -s ours am: 4e13bf0e  -s ours
am: 432cdb63  -s ours

Change-Id: Ia4dffeb6a8c0684ac05e051e01e17b0ef562cb72