Introduce ParallelDownloadJob.

content/browser/download/download_job.h

 // 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.
 
 #ifndef CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_JOB_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_JOB_H_
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/download_danger_type.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 
 namespace content {
+
+class DownloadItemImpl;
 class WebContents;
 
-// Unknown download progress.
-extern const int kDownloadProgressUnknown;
-
-// Unknown download speed.
-extern const int kDownloadSpeedUnknown;
-
-// DownloadJob contains internal download logic.
-// The owner of DownloadJob(e.g DownloadItemImpl) should implement
-// DownloadJob::Manager to be informed with important changes from
-// DownloadJob and modify its states accordingly.
+// DownloadJob lives on UI thread and subclasses implement actual download logic
+// and interact with DownloadItemImpl.
+// The base class is a friend class of DownloadItemImpl.
 class CONTENT_EXPORT DownloadJob {
  public:
-  // The interface used to interact with the owner of the download job.
-  class CONTENT_EXPORT Manager {
-   public:
-    // Called when |download_job| becomes actively download data.
-    virtual void OnSavingStarted(DownloadJob* download_job) = 0;
-
-    // Called when |download_job| is interrupted.
-    virtual void OnDownloadInterrupted(DownloadJob* download_job,
-                                       DownloadInterruptReason reason) = 0;
-
-    // Called when |download_job| is completed and inform the manager.
-    virtual void OnDownloadComplete(DownloadJob* download_job) = 0;
-
-    // Sets the download danger type.
-    virtual void SetDangerType(DownloadDangerType danger_type) = 0;
-  };
-
   DownloadJob();
   virtual ~DownloadJob();
 
-  DownloadJob::Manager* manager() { return manager_; }
-
-  // Called when DownloadJob is attached to DownloadJob::Manager.
-  // |manager| can be nullptr.
-  virtual void OnAttached(DownloadJob::Manager* manager);
-
-  // Called before DownloadJob is detached from its manager.
-  virtual void OnBeforeDetach();
+  // Attach the download item to this job.
+  void Attach(DownloadItemImpl* download_item);
 
   // Download operations.
+  virtual void Start() = 0;
   virtual void Cancel(bool user_cancel) = 0;
   virtual void Pause() = 0;
   virtual void Resume() = 0;
 
-  // Return if the download file can be opened.
-  // See |DownloadItem::CanOpenDownload|.
-  virtual bool CanOpen() const = 0;
-
-  // Return if the download job can be resumed.
-  virtual bool CanResume() const = 0;
-
-  // See |DownloadItem::CanShowInFolder|.
-  virtual bool CanShowInFolder() const = 0;
-
-  // Return if the download job is actively downloading.
-  virtual bool IsActive() const = 0;
-
-  // Return if the download job is paused.
-  virtual bool IsPaused() const = 0;
-
-  // Return a number between 0 and 100 to represent the percentage progress of
-  // the download. Return |kDownloadProgressUnknown| if the progress is
-  // indeterminate.
-  virtual int PercentComplete() const = 0;
-
-  // Return the estimated current download speed in bytes per second.
-  // Or return kDownloadSpeedUnknown if the download speed is not measurable.
-  virtual int64_t CurrentSpeed() const = 0;
-
-  // Set the estimated remaining time of the download to |remaining| and return
-  // true if time remaining is available, otherwise return false.
-  virtual bool TimeRemaining(base::TimeDelta* remaining) const = 0;
-
   // Return the WebContents associated with the download. Usually used to
   // associate a browser window for any UI that needs to be displayed to the
   // user.
   // Or return nullptr if the download is not associated with an active
   // WebContents.
   virtual WebContents* GetWebContents() const = 0;
 
-  // Print the debug string including internal states of the download job.
-  virtual std::string DebugString(bool verbose) const = 0;
+ protected:
+  void InitializeDownloadFile() const;
 
- protected:
-  // Mark the download as being active.
-  void StartedSavingResponse();
-
-  // Mark the download as interrupted.
-  void Interrupt(DownloadInterruptReason reason);
-
-  // Mark the download job as completed.
-  void Complete();
-
-  // Owner of this DownloadJob, Only valid between OnAttached() and
-  // OnBeforeDetach(), inclusive. Otherwise set to nullptr.
-  DownloadJob::Manager* manager_;
+  DownloadItemImpl* download_item_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DownloadJob);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_JOB_H_