Reland r288013: First cut at "content handling" support in Mojo.

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/services/public/interfaces/network/url_loader.mojom"
 
 module mojo {
 
-// Applications vend Services through the ServiceProvider interface. Services
-// implement Interfaces.
-[Client=Shell]
-interface Application {
-  AcceptConnection(string requestor_url, ServiceProvider provider);
+interface ContentHandler {
+  OnConnect(string url,
+            URLResponse url_response,
+            ServiceProvider service_provider);
 };
 
 }