bug 1058698 - split content/worker for e10s

and use the new one in page-mod
Merge pull request #1681 from zombie/1058698-split-worker

bug 1058698 - split content/worker for e10s, r=@Mossop
Bug 1088641: Strip all but the low-bytes of characters when calling base64.encode without a charset.
Merge pull request #1683 from Mossop/bug1088641

Bug 1088641: Strip all but the low-bytes of characters when calling base64.encode without a charset. r=@erikvold