Fix integer overflow in utf{16,32}_to_utf8_length am: f0a43dede9 am: 33abf90994 am: 789673b15c am: 1436927851 am: d70e582d67 am: 62d5a78df3
am: 5b37a8ce87

Change-Id: I9957d042e4b309f8071fe08c03177401051ec926