Merge "Remove unused utf8_length()." am: 52dac2f8b7 am: 0ee0648569 am: a7f8cdbfff

Original change: https://android-review.googlesource.com/c/platform/system/core/+/1474916

Change-Id: I0979c1e0aff9016266efdce738dc92934bd37c3e