Introduce ParallelDownloadJob.

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 "content/browser/download/download_item_impl.h"
+
 namespace content {
 
-// Unknown download progress.
-const int kDownloadProgressUnknown = -1;
-
-// Unknown download speed.
-const int kDownloadSpeedUnknown = -1;
-
-DownloadJob::DownloadJob() : manager_(nullptr) {}
+DownloadJob::DownloadJob(DownloadItemImpl* download_item)
+    : download_item_(download_item), is_paused_(false) {}
 
 DownloadJob::~DownloadJob() = default;
 
-void DownloadJob::OnAttached(DownloadJob::Manager* manager) {
-  DCHECK(!manager_) << "DownloadJob::Manager has already been attached.";
-  manager_ = manager;
+void DownloadJob::Pause() {
+  is_paused_ = true;
 }
 
-void DownloadJob::OnBeforeDetach() {
-  manager_ = nullptr;
+void DownloadJob::Resume(bool resume_request) {
+  is_paused_ = false;
 }
 
-void DownloadJob::StartedSavingResponse() {
-  if (manager_)
-    manager_->OnSavingStarted(this);
-}
-
-void DownloadJob::Interrupt(DownloadInterruptReason reason) {
-  if (manager_)
-    manager_->OnDownloadInterrupted(this, reason);
-}
-
-void DownloadJob::Complete() {
-  if (manager_)
-    manager_->OnDownloadComplete(this);
+void DownloadJob::StartDownload() const {
+  download_item_->StartDownload();
 }
 
 }  // namespace content