Fix paste sequence in Firefox

It appears that if the pasteTarget is given focus too close to the
range being set it may not take effect in time. Moving up to before
any of the selection setting logic seems to fix the issue.

Bug: 58283
Change-Id: I9bfb0ab6952863496fb3548e6804cb347d52cc57
(cherry picked from commit 333166e818ca949763136296fc78f8eadf348542)