Glue parallel download job and download file together.

content/browser/download/parallel_download_utils.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_UTILS_H_
 #define CONTENT_BROWSER_DOWNLOAD_PARALLEL_DOWNLOAD_UTILS_H_
 
 #include <vector>
 
+#include "content/browser/download/download_create_info.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/download_item.h"
 
 namespace content {
 
+// Return if the download should be a parallel download.
+CONTENT_EXPORT bool ShouldUseParallelDownload(
+    const DownloadCreateInfo& create_info);
+
+// Return the slices to download for the remaining content.
+// This function chunks the content into slices.
+CONTENT_EXPORT std::vector<DownloadItem::ReceivedSlice>
+FindSlicesForRemainingContent(int64_t bytes_received,
+                              int64_t total_bytes,
+                              int request_count);
+
 // Given an array of slices that are received, returns an array of slices to
 // download. |received_slices| must be ordered by offsets.
 CONTENT_EXPORT std::vector<DownloadItem::ReceivedSlice> FindSlicesToDownload(
     const std::vector<DownloadItem::ReceivedSlice>& received_slices);
 
 // Finch configuration utilities.
 //
 // Get the minimum slice size to use parallel download from finch configuration.
 // A slice won't be further chunked into smaller slices if the size is less
 // than the minimum size.
 CONTENT_EXPORT int64_t GetMinSliceSizeConfig();
 
 // Get the request count for parallel download from finch configuration.
 CONTENT_EXPORT int GetParallelRequestCountConfig();
 
 }  //  namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_PARALLEL_DOWNLOAD_UTILS_H_