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)
+    return;

[David Trainor- moved to gerrit, 2017/03/14 17:59:10]

When do we expect this to happen?

[xingliu, 2017/03/14 18:26:31]

Done, added a VLOG.

download_file is invalidated when DownloadItemImpl calls ReleaseDownloadFile.
 
It happens if the download is interrupted or complete, or restart a download
after user cancel the download.

The AddByteStream still may be called since the server response may arrive later
after something goes wrong or the original request complete the download.

We probably need to test this when put everything together. A cancel call may be
needed to kill the url_request in job class.

[David Trainor- moved to gerrit, 2017/03/17 07:15:27]

sg.  add a TODO to investigate/file a bug?

[xingliu, 2017/03/17 19:08:25]

Done.

+
+  // The life cycle of download file is controlled by download item, 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