Bug 978005 - [email] Fix usage of Bareword DOM constructors TextDecoder and TextEncoder. r=asuth

land https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/288
Merge pull request #16731 from asutherland/email-fix-bare

Bug 978005 - [email] Fix usage of Bareword DOM constructors TextDecoder and TextEncoder. r=asuth