Introduce ParallelDownloadJob.

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);
+  ~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;
+
+ private:
+  // Used to perform operations on network request.
+  // Can be null on interrupted download.
+  std::unique_ptr<DownloadRequestHandleInterface> request_handle_;
+
+  DISALLOW_COPY_AND_ASSIGN(DownloadJobImpl);
+};
+
+}  //  namespace content
+
+#endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_JOB_IMPL_H_