Don't create parallel request until download file is initialized

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) {}
+    : download_item_(download_item),
+      is_paused_(false),
+      weak_ptr_factory_(this) {}
 
 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::Start(DownloadFile* download_file_,
+                        const DownloadFile::InitializeCallback& callback,
+                        const DownloadItem::ReceivedSlices& received_slices) {
+  BrowserThread::PostTask(
+      BrowserThread::FILE, FROM_HERE,
+      base::Bind(&DownloadFile::Initialize,
+                 // Safe because we control download file lifetime.
+                 base::Unretained(download_file_),
+                 base::Bind(&DownloadJob::OnDownloadFileInitialized,
+                            weak_ptr_factory_.GetWeakPtr(), callback),
+                 base::Bind(&DownloadJob::CancelRequestWithOffset,
+                            weak_ptr_factory_.GetWeakPtr()),
+                 received_slices, IsParallelizable()));
+}
+
+void DownloadJob::OnDownloadFileInitialized(
+    const DownloadFile::InitializeCallback& callback,
+    DownloadInterruptReason result) {
+  callback.Run(result);
 }
 
 bool 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 false;
 
   // 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));
   return true;
 }
 
 void DownloadJob::CancelRequestWithOffset(int64_t offset) {
   NOTREACHED();
 }
 
 bool DownloadJob::IsParallelizable() const {
   return false;
 }
 
 }  // namespace content