Merge pull request #10438 from airpingu/bug-880648-mms-accented-characters-part-2

Bug 880648 - [MMS] Accented characters are not correctly sent/received in a MMS (part 2, content blob must be encoded by utf-8). r=steveck-chung, a=leo+(cherry picked from commit 70e1de2de1722e6ecd131d68a0a403f5e1054166)