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

Change-Id: If605b2b03790475250c3a5c9627b9f6177c01226