String16::remove - avoid overflow am: 4048e49956 am: 107f18cb61 am: 9be245c3f0 am: 64fb5012b8 am: 4e27b6992b am: 26b81f59d2 am: 8367a666b5

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/core/+/11619802

Change-Id: Ic25dca55b553b062edc4ced44ddef68b96428906