The .in.in file was added to the repo in 8bdfa6a4e56f. Then Gary added the .in file to POTFILES.in in 1d98555... but I think it should actually be the .in.in file, right?
/* pidgin
*
* Pidgin is the legal property of its developers, whose names are too numerous
* to list here. Please refer to the COPYRIGHT file distributed with this
* source distribution.
*
* This program is free software; you can redistribute it and/or modify
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA
{&priv->larger_size,"ToggleLarger",PIDGIN_STOCK_TOOLBAR_TEXT_LARGER,N_("<span size='larger'>Larger</span>"),N_("Increase Font Size"),do_big,FALSE},
#if 0
{&priv->normal_size, "ToggleNormal", NULL, N_("Normal"), N_("Normal Font Size"), NULL, FALSE},
#endif
{&priv->smaller_size,"ToggleSmaller",PIDGIN_STOCK_TOOLBAR_TEXT_SMALLER,N_("<span size='smaller'>Smaller</span>"),N_("Decrease Font Size"),do_small,FALSE},