This code needs to move out of PrepareResizeReflow() (and things that
trigger code in it) because PrepareResizeReflow is conditioned on the
block itself resizing.
The reftest is based on a test by Jesse Ruderman <jruderman@gmail.com>.
The reftest fails without the patch and passes with the patch.
--HG--
extra : transplant_source : %E9%5E%97zE%A4%60n%8C%DD%F8K-%01%F3fF%E8%C9K