Provide route ID via URLLoaderFactory

content/common/url_loader_factory.mojom

 // Copyright 2016 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.
 
 module content.mojom;
 
 import "url_loader.mojom";
 
 interface URLLoaderFactory {
   // Creats a URLLoader and starts loading with the given |request|. |client|'s
   // method will be called when certain events related to that loading
   // (e.g., response arrival) happen. |request_id| is for compatibility with
   // the existing Chrome IPC.
   CreateLoaderAndStart(URLLoader& loader,
+                       int32 routing_id,
                        int32 request_id,
                        URLRequest request,
                        URLLoaderClient client);
 };