main: Move 'toggle-recording' binding into the shell

The keybinding to toggle the screen recorder was implemented as a
signal on MetaScreen, as keybindings could only be defined in mutter
core. As this is no longer the case, we can move the binding into the
shell where it belongs.

https://bugzilla.gnome.org/show_bug.cgi?id=674377

js/ui/main.js

@@ -101,8 +101,11 @@ function _createGDMSession() {
 
 function _initRecorder() {
     let recorderSettings = new Gio.Settings({ schema: 'org.gnome.shell.recorder' });
+    let bindingSettings = new Gio.Settings({ schema: 'org.gnome.shell.keybindings' });
 
-    global.screen.connect('toggle-recording', function() {
+    global.display.add_keybinding('toggle-recording',
+                                  bindingSettings,
+                                  Meta.KeyBindingFlags.NONE, function() {
         if (recorder == null) {
             recorder = new Shell.Recorder({ stage: global.stage });
         }