Revert "Faster and simpler replace in SSB"

Bug 6300658

This change reveals a weird race condition where sometimes the
text is entered twice. Adding a debugger slows down everything,
and the problem is no longer reproducable. Reverting for now.

This reverts commit ebd9a23817052c4d2aaa1058efa2b80b08003d4a.
1 file changed