Make textarea in photo uploads autoresize

As per Kaity's request. This abstracts what we were using for the editor
with one additional fix.

Previously, the editor would jump back to the top of the overlay if
textarea was larger than screen height. This shouldn't happen anymore.

Change-Id: I93812bf1bd89fec03ea76470254692accb00c4a2
Merge "Make textarea in photo uploads autoresize"