Bug 1025711 - [email/sanitizer] Quiet bleach.js CSS parser errors. r=jrburke

land https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/314
Merge pull request #20652 from asutherland/email-quiet-css-errors

Bug 1025711 - [email/sanitizer] Quiet bleach.js CSS parser errors. r=jrburke