DO NOT MERGE Add bound checks to utf16_to_utf8 am: 0d9d569c26 am: edce8ad060 am: 4f24f218dc  -s ours am: 2c6f342c35
am: 40e8702523

Change-Id: Ie67f0d9f36a72edaf2ebf2cc49c213fa813bde14