DO NOT MERGE Add bound checks to utf16_to_utf8 am: 0d9d569c26 am: edce8ad060 am: 4f24f218dc  -s ours am: 2c6f342c35 am: 40e8702523 am: 0b0374c502 am: cdafc2541c  -s ours
am: c146d05562

Change-Id: Ib82bbc8345f8fb4314d19bc2360f6bf4f27a414d