add a download slices table into history download db

components/history/core/browser/download_job_info.h

Index: components/history/core/browser/download_job_info.h
diff --git a/components/history/core/browser/download_job_info.h b/components/history/core/browser/download_job_info.h
new file mode 100644
index 0000000000000000000000000000000000000000..bfede58cc8673a58640295990420a2508300f0e9
--- /dev/null
+++ b/components/history/core/browser/download_job_info.h
@@ -0,0 +1,58 @@
+// 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 COMPONENTS_HISTORY_CORE_BROWSER_DOWNLOAD_JOB_INFO_H_
+#define COMPONENTS_HISTORY_CORE_BROWSER_DOWNLOAD_JOB_INFO_H_
+
+#include <stdint.h>
+#include <string>
+
+#include "components/history/core/browser/download_types.h"
+
+namespace history {
+
+// Contains the download job information that is stored in the download
+// system's persistent store (or refers to it). Each download item can have
+// multiple download job associated with it, with each job has its own
+// start position.
+struct DownloadJobInfo {
+  DownloadJobInfo();
+  DownloadJobInfo(DownloadId id,
+                  int job_id,
+                  int64_t start_position,
+                  int64_t length,
+                  int64_t received_bytes,
+                  DownloadState state,
+                  DownloadInterruptReason interrupt_reason);
+  DownloadJobInfo(const DownloadJobInfo& other);
+  ~DownloadJobInfo();
+
+  bool operator==(const DownloadJobInfo&) const;
+
+  // The id of the download in the database. Not changed by UpdateDownload().
+  DownloadId id;
+
+  // Job id of the download.
+  int job_id;
+
+  // Start position of the download request.
+  int64_t start_position;
+
+  // Data length to download. If length < 0, download should continue until
+  // the stream reaches the end.
+  int64_t length;
+
+  // The number of bytes received (so far).
+  int64_t received_bytes;
+
+  // The current state of the download.
+  DownloadState state;
+
+  // The reason the download was interrupted, if state == kStateInterrupted.
+  DownloadInterruptReason interrupt_reason;
+};
+
+}  // namespace history
+
+#endif  // COMPONENTS_HISTORY_CORE_BROWSER_DOWNLOAD_JOB_INFO_H_