GUACAMOLE-352: Explicitly listen to the input sink.

guacamole/src/main/webapp/app/index/controllers/indexController.js

@@ -88,6 +88,7 @@ angular.module('index').controller('indexController', ['$scope', '$injector',
 
     // Create event listeners at the global level
     var keyboard = new Guacamole.Keyboard($document[0]);
+    keyboard.listenTo(sink.getElement());
 
     // Broadcast keydown events
     keyboard.onkeydown = function onkeydown(keysym) {