Implement ServiceWorkerFetchDispatcher::MaybeStartNavigationPreload().

content/browser/loader/resource_dispatcher_host_impl.h

 // Copyright (c) 2012 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.
 
 // This is the browser side of the resource dispatcher, it receives requests
 // from the child process (i.e. [Renderer, Plugin, Worker]ProcessHost), and
 // dispatches them to URLRequests. It then forwards the messages from the
 // URLRequests back to the correct process for handling.
 //
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
@@ skipping 319 matching lines @@
   // called to initialize the request before calling this function.
   void BeginURLRequest(std::unique_ptr<net::URLRequest> request,
                        std::unique_ptr<ResourceHandler> handler,
                        bool is_download,
                        bool is_content_initiated,
                        bool do_not_prompt_for_login,
                        ResourceContext* context);
 
   bool is_shutdown() const { return is_shutdown_; }
 
+  // Creates a new request ID for browser initiated requests. See the comments
+  // of |request_id_| for the details.
+  int MakeRequestID() { return --request_id_; }

[mmenke, 2016/10/19 14:56:02]

Could you make this DCHECK that we're on the IO thread, and move it to the cc
file?

[horo, 2016/10/19 15:18:53]

Done.

+
  private:
   friend class ResourceDispatcherHostTest;
 
   FRIEND_TEST_ALL_PREFIXES(ResourceDispatcherHostTest,
                            TestBlockedRequestsProcessDies);
   FRIEND_TEST_ALL_PREFIXES(ResourceDispatcherHostTest,
                            CalculateApproximateMemoryCost);
   FRIEND_TEST_ALL_PREFIXES(ResourceDispatcherHostTest,
                            DetachableResourceTimesOut);
   FRIEND_TEST_ALL_PREFIXES(ResourceDispatcherHostTest,
@@ skipping 407 matching lines @@
 
   // Points to the registered download handler intercept.
   CreateDownloadHandlerIntercept create_download_handler_intercept_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourceDispatcherHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_RESOURCE_DISPATCHER_HOST_IMPL_H_