renaming once_displayed into after_displayed

IPython/html/static/widgets/js/widget.js

@@ -390,7 +390,7 define(["widgets/js/manager",
             this.model.save_changes(this.callbacks());
         },
 
-        once_displayed: function (callback, context) {
+        after_displayed: function (callback, context) {
             // Calls the callback right away is the view is already displayed
             // otherwise, register the callback to the 'displayed' event.
             if (this.is_displayed) {

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

@@ -38,7 +38,7 define([
             this.$el.append(view.$el);
 
             // Trigger the displayed event once this view is displayed.
-            this.once_displayed(function() {
+            this.after_displayed(function() {
                 view.trigger('displayed');
             });
         },
@@ -230,7 +230,7 define([
             this.$body.append(view.$el);
 
             // Trigger the displayed event once this view is displayed.
-            this.once_displayed(function() {
+            this.after_displayed(function() {
                 view.trigger('displayed');
             });
         },