Don't create parallel request until download file is initialized

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 <unordered_map>
 #include <vector>
@@ skipping 12 matching lines @@
 class CONTENT_EXPORT ParallelDownloadJob : public DownloadJobImpl,
                                            public DownloadWorker::Delegate {
  public:
   ParallelDownloadJob(
       DownloadItemImpl* download_item,
       std::unique_ptr<DownloadRequestHandleInterface> request_handle,
       const DownloadCreateInfo& create_info);
   ~ParallelDownloadJob() override;
 
   // DownloadJobImpl implementation.
-  void Start() override;
   void Cancel(bool user_cancel) override;
   void Pause() override;
   void Resume(bool resume_request) override;
   void CancelRequestWithOffset(int64_t offset) override;
 
  protected:
+  // DownloadJobImpl implementation.
+  void OnDownloadFileInitialized(
+      const DownloadFile::InitializeCallback& callback,
+      DownloadInterruptReason result) override;
+
   // Virtual for testing.
   virtual int GetParallelRequestCount() const;
   virtual int64_t GetMinSliceSize() const;
   virtual int GetMinRemainingTimeInSeconds() const;
 
   using WorkerMap =
       std::unordered_map<int64_t, std::unique_ptr<DownloadWorker>>;
 
   // Map from the offset position of the slice to the worker that downloads the
   // slice.
@@ skipping 39 matching lines @@
 
   // If the download progress is canceled.
   bool is_canceled_;
 
   DISALLOW_COPY_AND_ASSIGN(ParallelDownloadJob);
 };
 
 }  //  namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_PARALLEL_DOWNLOAD_JOB_H_