Introduce ParallelDownloadJob.

content/browser/download/url_downloader.h

 // Copyright 2015 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_URL_DOWNLOADER_H_
 #define CONTENT_BROWSER_DOWNLOAD_URL_DOWNLOADER_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/memory/weak_ptr.h"
 #include "content/browser/download/download_request_core.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "content/public/browser/download_save_info.h"
 #include "content/public/browser/download_url_parameters.h"
 #include "content/public/common/referrer.h"
 #include "net/url_request/redirect_info.h"
 #include "net/url_request/url_request.h"
 
 namespace content {
 class ByteStreamReader;
 struct DownloadCreateInfo;
-class DownloadManagerImpl;
 
 class UrlDownloader : public net::URLRequest::Delegate,
                       public DownloadRequestCore::Delegate {
  public:
+  // Implemented by the owner of UrlDownloader, functions need to be called on
+  // UI thread.
+  class Delegate {
+   public:
+    // Called after response is handled and the byte stream is established.
+    virtual void OnUrlDownloaderStarted(
+        std::unique_ptr<DownloadCreateInfo> download_create_info,
+        std::unique_ptr<ByteStreamReader> stream_reader,
+        const DownloadUrlParameters::OnStartedCallback& callback) = 0;
+
+    // Called after the connection is cannceled or finished.
+    virtual void OnUrlDownloaderStopped(UrlDownloader* downloader) = 0;
+  };
+
   UrlDownloader(std::unique_ptr<net::URLRequest> request,
-                base::WeakPtr<DownloadManagerImpl> manager);
+                base::WeakPtr<Delegate> delegate);
   ~UrlDownloader() override;
 
   static std::unique_ptr<UrlDownloader> BeginDownload(
-      base::WeakPtr<DownloadManagerImpl> download_manager,
+      base::WeakPtr<UrlDownloader::Delegate> delegate,
       std::unique_ptr<net::URLRequest> request,
       const Referrer& referrer);
 
  private:
   class RequestHandle;
 
   void Start();
 
   // URLRequest::Delegate:
   void OnReceivedRedirect(net::URLRequest* request,
@@ skipping 15 matching lines @@
   void PauseRequest();
   void ResumeRequest();
   void CancelRequest();
 
   // Called when the UrlDownloader is done with the request. Posts a task to
   // remove itself from its download manager, which in turn would cause the
   // UrlDownloader to be freed.
   void Destroy();
 
   std::unique_ptr<net::URLRequest> request_;
-  base::WeakPtr<DownloadManagerImpl> manager_;
+
+  // Live on UI thread, post task to call |delegate_| functions.
+  base::WeakPtr<Delegate> delegate_;
   DownloadRequestCore core_;
 
   base::WeakPtrFactory<UrlDownloader> weak_ptr_factory_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_URL_DOWNLOADER_H_