Add handle_key stub to gonk port

ports/gonk/src/window.rs

@@ -13,6 +13,7 @@ use layers::platform::surface::NativeGraphicsMetadata;
 use libc::c_int;
 use msg::compositor_msg::{Blank, IdlePaintState};
 use msg::compositor_msg::{ReadyState, PaintState};
+use msg::constellation_msg::{Key, KeyModifiers};
 use msg::constellation_msg::LoadData;
 use std::cell::Cell;
 use std::comm::Receiver;
@@ -810,6 +811,9 @@ impl WindowMethods for Window {
         }
     }
 
+    fn handle_key(&self, _: Key, _: KeyModifiers) {
+    }
+
     fn create_compositor_channel(window: &Option<Rc<Window>>)
                                  -> (Box<CompositorProxy+Send>, Box<CompositorReceiver>) {
         let (sender, receiver) = channel();