Remove message promise.

IPython/html/static/services/kernels/comm.js

@@ -131,11 +131,6 b' define(['
         this.target_name = target_name;
         this.comm_id = comm_id || utils.uuid();
         this._msg_callback = this._close_callback = null;
-
-        var that = this;
-        this.msg_promise = new Promise(function(resolve, reject) {
-            that.resolve_msg_promise = resolve;
-        });
     };
     
     // methods for sending messages
@@ -171,7 +166,6 b' define(['
     
     Comm.prototype.on_msg = function (callback) {
         this._register_callback('msg', callback);
-        this.resolve_msg_promise();
     };
     
     Comm.prototype.on_close = function (callback) {
@@ -192,11 +186,7 b' define(['
     };
     
     Comm.prototype.handle_msg = function (msg) {
-        var that = this;
-        this.msg_promise = this.msg_promise.then(function() {
             that._maybe_callback('msg', msg);
-            return Promise.resolve();
-        });
     };
     
     Comm.prototype.handle_close = function (msg) {

IPython/html/static/widgets/js/manager.js

@@ -183,7 +183,7 b' define(['
 
     WidgetManager.prototype._handle_comm_open = function (comm, msg) {
         // Handle when a comm is opened.
-        this.create_model({
+        return this.create_model({
             model_name: msg.content.data.model_name, 
             model_module: msg.content.data.model_module, 
             comm: comm}).catch($.proxy(console.error, console));