Rub some butter on dictionary list scrolling.

The default implementation for preferences refuses to
cache the views for custom preferences at all. We can
do it, but the system won't do it for us, so this does it.
This makes the screen scrolling smooth again.

Incidentally it also fixes the bug where the button may
not animate on the first element.

Bug: 8882722
Bug: 8883108
Change-Id: I9b2306ac4bf93761a808ebfee3477a65f017cddf