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: 0f44e904e8

Change-Id: Ia616f9694eb0edf187f6a63d7001bf7b0c6f995a