Linux: Remove GTK+ dependency and add initial Aura/X11 implementation (issue #1258)

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk/cef3@1708 5089003a-bbd8-11dd-ad1f-f1f9622dbc98
Fix revision #1708 compile error.

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk/cef3@1709 5089003a-bbd8-11dd-ad1f-f1f9622dbc98