libutils/Unicode.cpp: Correct length computation and add checks for utf16->utf8 am: 53473c1607 am: 41e6690d0c am: 29ccafe5f0 am: fd7bd2dfef am: 498ffa62c5
am: 5e4ebd02d4

Change-Id: Ib2eb019edba21cd3ba3e22d745818d30c912ce62