String16: remove integer overflows Bug: 73826242 Test: manual Change-Id: I32e13d61b944c1a527cf2d95473552d246e322be Merged-In: I32e13d61b944c1a527cf2d95473552d246e322be (cherry picked from commit d0648d8dc61fe9ac39d2cd150a332b385a334bdc)