Reducing tab size

[shellreef at gmail.com]

> Yeah.. I've been complaining about this the past 5 days or so in
> #guification.  I just did a pull and the conversation dialog size is not
> getting saved. Default size each time the dialog is closed and re-opened
> (Including restarting pidgin with the resized conversation dialog still
> opened) shown in screenshot.
>
> http://pidgin.dennisr.net/screenshot-small_convo_dialog.png
I've been seeing this too, since I propagated from branch
im.pidgin.pidgin head 128e100bae27b44dc77c5db5be0151b0fceaea8f. It
doesn't happen in 2.1.0.