String16::remove - avoid overflow

Bug: 156999009
Test: libutils_test (cases added)
Change-Id: Iad46d95d9848928ba81000090b2fe9aec1e5eaac
Merged-In: Iad46d95d9848928ba81000090b2fe9aec1e5eaac
(cherry picked from commit f251c1c581f2d1b9940e60e756315c5e15443990)
(cherry picked from commit 9a9c8910e9296c9dc8d79c37f589895f5a2a836c)
(cherry picked from commit 4048e49956a2dfd49af3adf0f78881bf15f3550f)
1 file changed