mojo: Update content handler API

mojo/services/public/interfaces/content_handler/content_handler.mojom

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import "mojo/public/interfaces/application/service_provider.mojom";
+import "mojo/public/interfaces/application/shell.mojom";
 import "mojo/services/public/interfaces/network/url_loader.mojom";
 
 module mojo {
 
 interface ContentHandler {
-  OnConnect(string requestor_url,
-            URLResponse response,
-            ServiceProvider&? service_provider);
+  StartApplication(Shell shell, URLResponse response);
 };
 
 }