unnecessary context variable specify

IPython/html/static/widgets/js/widget_container.js

@@ -38,7 +38,9 b' define(['
             this.$el.append(view.$el);
 
             // Trigger the displayed event once this model is displayed.
-            this.once_displayed(function() { view.trigger('displayed'); }, this);
+            this.once_displayed(function() {
+                view.trigger('displayed');
+            });
         },
         
         update: function(){
@@ -230,7 +232,7 b' define(['
             // Trigger the displayed event once this model is displayed.
             this.once_displayed(function() { 
                 view.trigger('displayed'); 
-            }, this);
+            });
         },
         
         update: function(){