gtk: Make use of gtk signal macros in AddLanguageDialog.
gtk: Make use of gtk signal macros in AddLanguageDialog.

BUG=None
TEST=manually

Patch from Thiago Farina <thiago.farina@gmail.com>

Review URL: http://codereview.chromium.org/1903002

git-svn-id: http://src.chromium.org/svn/trunk/src@46507 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 1cdb72ec77d847863b24202f1664cd732523435b
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser