Previously we did the equivalent of a $('.message_comp').child('input'),
which does not search beyond the first level.
In addition, using a comma in a selector is essentially an AND, which
means the narrow search only applied to elements of the 'input' class.
So when debugging we saw a bunch of elements being selected and that hid
the bug for a bit.
Now we do a .find instead which will ensure we blur the correct
elements.
This closes trac #1045.
(imported from commit f44383ee9fc93406d031589ef914f5a003334ea7)