Use require.js to load widget manager.

IPython/html/static/notebook/js/widgets/model_container.js

@@ -1,3 +1,4
+require(["notebook/js/widget"], function () {
 var ContainerModel = IPython.WidgetModel.extend({});
 IPython.notebook.widget_manager.register_widget_model('container_widget', ContainerModel);
 
@@ -15,3 +16,4 var ContainerView = IPython.WidgetView.extend({
 });
 
 IPython.notebook.widget_manager.register_widget_view('ContainerView', ContainerView);
+});
  No newline at end of file

IPython/html/static/notebook/js/widgets/model_float_range.js

@@ -1,3 +1,4
+require(["notebook/js/widget"], function () {
 var FloatRangeWidgetModel = IPython.WidgetModel.extend({});
 IPython.notebook.widget_manager.register_widget_model('FloatRangeWidgetModel', FloatRangeWidgetModel);
 
@@ -117,3 +118,4 var FloatTextView = IPython.WidgetView.extend({
 });
 
 IPython.notebook.widget_manager.register_widget_view('FloatTextView', FloatTextView);
+});
  No newline at end of file

IPython/html/static/notebook/js/widgets/model_int_range.js

@@ -1,3 +1,4
+require(["notebook/js/widget"], function () {
 var IntRangeWidgetModel = IPython.WidgetModel.extend({});
 IPython.notebook.widget_manager.register_widget_model('IntRangeWidgetModel', IntRangeWidgetModel);
 
@@ -115,3 +116,4 var IntTextView = IPython.WidgetView.extend({
 });
 
 IPython.notebook.widget_manager.register_widget_view('IntTextView', IntTextView);
+});
  No newline at end of file

IPython/html/static/notebook/js/widgets/model_selection.js

@@ -1,3 +1,4
+require(["notebook/js/widget"], function () {
 var SelectionWidgetModel = IPython.WidgetModel.extend({});
 IPython.notebook.widget_manager.register_widget_model('SelectionWidgetModel', SelectionWidgetModel);
 
@@ -126,3 +127,4 var RadioButtonView = IPython.WidgetView.extend({
 });
 
 IPython.notebook.widget_manager.register_widget_view('RadioButtonView', RadioButtonView);
+});
  No newline at end of file

IPython/html/static/notebook/js/widgets/model_string.js

@@ -1,3 +1,4
+require(["notebook/js/widget"], function () {
 var StringWidgetModel = IPython.WidgetModel.extend({});
 IPython.notebook.widget_manager.register_widget_model('StringWidgetModel', StringWidgetModel);
 
@@ -72,3 +73,5 var TextboxView = IPython.WidgetView.extend({
 });
 
 IPython.notebook.widget_manager.register_widget_view('TextboxView', TextboxView);
+
+});
  No newline at end of file