Glue parallel download job and download file together.

content/browser/download/download_job.cc

 // 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.
 
 #include "content/browser/download/download_job.h"
 
+#include "base/bind_helpers.h"
+#include "content/browser/download/download_file.h"
 #include "content/browser/download/download_item_impl.h"
+#include "content/public/browser/browser_thread.h"
 
 namespace content {
 
 DownloadJob::DownloadJob(DownloadItemImpl* download_item)
     : download_item_(download_item), is_paused_(false) {}
 
 DownloadJob::~DownloadJob() = default;
 
 void DownloadJob::Pause() {
   is_paused_ = true;
 }
 
 void DownloadJob::Resume(bool resume_request) {
   is_paused_ = false;
 }
 
 void DownloadJob::StartDownload() const {
   download_item_->StartDownload();
 }
 
+void DownloadJob::AddByteStream(std::unique_ptr<ByteStreamReader> stream_reader,
+                                int64_t offset,
+                                int64_t length) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DownloadFile* download_file = download_item_->download_file_.get();
+  if (!download_file) {
+    VLOG(1) << "Download file is released when byte stream arrived. Discard "
+               "the byte stream.";
+    return;
+  }
+
+  // download_file_ is owned by download_item_ on the UI thread and is always
+  // deleted on the FILE thread after download_file_ is nulled out.
+  // So it's safe to use base::Unretained here.
+  BrowserThread::PostTask(
+      BrowserThread::FILE, FROM_HERE,
+      base::Bind(&DownloadFile::AddByteStream, base::Unretained(download_file),
+                 base::Passed(&stream_reader), offset, length));
+}
+
 }  // namespace content