Added `method` property to messages from the front-end

IPython/html/static/notebook/js/widget.js

@@ -78,7 +78,7 b' define(["components/underscore/underscore-min",'
                 }
             }
             var callbacks = this._make_callbacks(cell);
-            var data = {'custom_content': content};
+            var data = {method: 'custom', custom_content: content};
             this.comm.send(data, callbacks);   
         },
 
@@ -156,7 +156,7 b' define(["components/underscore/underscore-min",'
                     if (selector === undefined) {
                         selector = '';
                     }
-                    
+
                     var class_list = msg.content.data.class_list;
                     this._execute_views_method(method, selector, class_list);
                     break;
@@ -253,7 +253,7 b' define(["components/underscore/underscore-min",'
                         }
                     }
 
-                    var data = {sync_method: method, sync_data: send_json};
+                    var data = {method: 'backbone', sync_method: method, sync_data: send_json};
 
                     var cell = null;
                     if (this.last_modified_view != undefined && this.last_modified_view != null) {

IPython/html/widgets/widget.py

@@ -113,16 +113,19 b' class Widget(LoggingConfigurable):'
     def _handle_msg(self, msg):
         """Called when a msg is recieved from the frontend"""
         data = msg['content']['data']
-        
+        method = data['method']
+
         # Handle backbone sync methods CREATE, PATCH, and UPDATE
-        if 'sync_method' in data and 'sync_data' in data:
-            sync_method = data['sync_method']
-            sync_data = data['sync_data']
-            self._handle_recieve_state(sync_data) # handles all methods
+        if method == 'backbone':
+            if 'sync_method' in data and 'sync_data' in data:
+                sync_method = data['sync_method']
+                sync_data = data['sync_data']
+                self._handle_recieve_state(sync_data) # handles all methods
 
         # Handle a custom msg from the front-end
-        if 'custom_content' in data:
-            self._handle_custom_msg(data['custom_content'])
+        elif method == 'custom':
+            if 'custom_content' in data:
+                self._handle_custom_msg(data['custom_content'])
 
 
     def _handle_custom_msg(self, content):