libutils/Unicode.cpp: Correct length computation and add checks for utf16->utf8 am: 3411dd4457 am: 01dbd1da64 am: 7c516d7080 am: 062c13e997  -s ours am: 254b45e573
am: cf76ba7f7b

Change-Id: I07a4b048841b0916d2f030ab4bc07f3da1e4aa8b