Add a delay to send the parallel requests.

content/browser/download/parallel_download_job.h

 // Copyright 2017 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.
 
 #ifndef CONTENT_BROWSER_DOWNLOAD_PARALLEL_DOWNLOAD_JOB_H_
 #define CONTENT_BROWSER_DOWNLOAD_PARALLEL_DOWNLOAD_JOB_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
+#include "base/timer/timer.h"
 #include "content/browser/download/download_job_impl.h"
 #include "content/browser/download/download_worker.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 // DownloadJob that can create concurrent range requests to fetch different
 // parts of the file.
 // The original request is hold in base class DownloadUrlJob.
 class CONTENT_EXPORT ParallelDownloadJob : public DownloadJobImpl {
@@ skipping 16 matching lines @@
   typedef std::vector<std::unique_ptr<DownloadWorker>> WorkerList;
 
   // Build multiple http requests for a new download,
   // the rest of the bytes starting from |bytes_received| will be equally
   // distributed to each connection, including the original connection.
   // the last connection may take additional bytes.
   void ForkRequestsForNewDownload(int64_t bytes_received,
                                   int64_t total_bytes,
                                   int request_count);
 
+  // Build parallel requests after a delay, to effectively measure the single
+  // stream bandwidth.
+  void BuildParallelRequestAfterDelay();
+
   // Build parallel requests to download the remaining slices.
   // TODO(qinmin): remove ForkRequestsForNewDownload() and move the logic into
   // this function.
   void BuildParallelRequests();
 
   // Create one range request, virtual for testing.
   virtual void CreateRequest(int64_t offset, int64_t length);
 
   // Information about the initial request when download is started.
   int64_t initial_request_offset_;
   int64_t initial_request_length_;
 
   // Subsequent tasks to send range requests.
   WorkerList workers_;
 
+  // Used to send parallel requests after a delay based on Finch config.
+  base::OneShotTimer timer_;
+
+  // If we have sent parallel requests.
+  bool requests_sent_;
+
   DISALLOW_COPY_AND_ASSIGN(ParallelDownloadJob);
 };
 
 }  //  namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_PARALLEL_DOWNLOAD_JOB_H_