Don't create parallel request until download file is initialized

content/browser/download/download_job_impl.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_DOWNLOAD_JOB_IMPL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_JOB_IMPL_H_
 
 #include "base/macros.h"
 #include "content/browser/download/download_item_impl.h"
 #include "content/browser/download/download_job.h"
 #include "content/browser/download/download_request_handle.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 class CONTENT_EXPORT DownloadJobImpl : public DownloadJob {
  public:
   DownloadJobImpl(
       DownloadItemImpl* download_item,
       std::unique_ptr<DownloadRequestHandleInterface> request_handle,
       bool is_parallizable);
   ~DownloadJobImpl() override;
 
   // DownloadJob implementation.
-  void Start() override;
   void Cancel(bool user_cancel) override;
   void Pause() override;
   void Resume(bool resume_request) override;
   WebContents* GetWebContents() const override;
   bool IsParallelizable() const override;
 
  private:
   // Used to perform operations on network request.
   // Can be null on interrupted download.
   std::unique_ptr<DownloadRequestHandleInterface> request_handle_;
 
   // Whether the download can be parallized.
   bool is_parallizable_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadJobImpl);
 };
 
 }  //  namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_JOB_IMPL_H_