[combo-box] Add function prototype to header file
[combo-box] Add function prototype to header file

pwithnall/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx