Set default view to None and never display widget with no view

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

@@ -422,8 +422,6 b' define(["widgets/js/manager",'
     });
 
 
-    widgetmanager.WidgetManager.register_widget_view('WidgetView', WidgetView);
-
     var DOMWidgetView = WidgetView.extend({
         initialize: function (parameters) {
             // Public constructor
@@ -595,7 +593,6 b' define(["widgets/js/manager",'
         },
     });
 
-    widgetmanager.WidgetManager.register_widget_view('DOMWidgetView', DOMWidgetView);
     
     var widget = {
         'WidgetModel': WidgetModel,

IPython/html/widgets/widget.py

@@ -100,7 +100,7 b' class Widget(LoggingConfigurable):'
     #-------------------------------------------------------------------------
     _model_name = Unicode('WidgetModel', help="""Name of the backbone model 
         registered in the front-end to create and sync this widget with.""")
-    _view_name = Unicode('WidgetView', help="""Default view registered in the front-end
+    _view_name = Unicode(None, allow_none=True, help="""Default view registered in the front-end
         to use to represent the widget.""", sync=True)
     comm = Instance('IPython.kernel.comm.Comm')
     
@@ -368,8 +368,8 b' class Widget(LoggingConfigurable):'
 
     def _ipython_display_(self, **kwargs):
         """Called when `IPython.display.display` is called on the widget."""
-        # Show view.  By sending a display message, the comm is opened and the
-        # initial state is sent.
+        # Show view.
+        if self._view_name is not None:
         self._send({"method": "display"})
         self._handle_displayed(**kwargs)