[GTK] Fix build error on GTK due to r138836
https://bugs.webkit.org/show_bug.cgi?id=106154

Patch by Michael Pruett <michael@68k.org> on 2013-01-04
Reviewed by Kentaro Hara.

* GNUmakefile.am:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@138882 268f45cc-cd09-0410-ab3c-d52691b4dbfc