Removed get_kernel method.

IPython/html/static/notebook/js/widgetmanager.js

@@ -185,7 +185,10 b''
             // for the message.  get_cell callbacks are registered for
             // widget messages, so this block is actually checking to see if the
             // message was triggered by a widget.
-            var kernel = this.get_kernel();
+            var kernel = null;
+            if (this.comm_manager !== null) {
+                kernel = this.comm_manager.kernel;
+            }
             if (kernel !== undefined && kernel !== null) {
                 var callbacks = kernel.get_callbacks_for_msg(msg_id);
                 if (callbacks !== undefined && 
@@ -247,15 +250,6 b''
         };
 
 
-        WidgetManager.prototype.get_kernel = function () {
-            if (this.comm_manager === null) {
-                return null;
-            } else {
-                return this.comm_manager.kernel;
-            }
-        };
-
-
         WidgetManager.prototype._handle_comm_open = function (comm, msg) {
             var widget_type_name = msg.content.target_name;
             var widget_model = new this._model_types[widget_type_name](this, comm.comm_id, comm);