downloads: add the ability to undo download removal.

content/browser/download/download_item_impl.h

 // Copyright (c) 2012 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_ITEM_IMPL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 79 matching lines @@
 
   // DownloadItem
   void AddObserver(DownloadItem::Observer* observer) override;
   void RemoveObserver(DownloadItem::Observer* observer) override;
   void UpdateObservers() override;
   void ValidateDangerousDownload() override;
   void StealDangerousDownload(const AcquireFileCallback& callback) override;
   void Pause() override;
   void Resume() override;
   void Cancel(bool user_cancel) override;
+  void MarkRemoved() override;
+  void UndoRemove() override;
   void Remove() override;
   void OpenDownload() override;
   void ShowDownloadInShell() override;
   uint32 GetId() const override;
   DownloadState GetState() const override;
   DownloadInterruptReason GetLastReason() const override;
   bool IsPaused() const override;
   bool IsTemporary() const override;
   bool CanResume() const override;
   bool IsDone() const override;
@@ skipping 164 matching lines @@
     // A request to resume this interrupted download is in progress.
     // Transitions from:
     //   INTERRUPTED_INTERNAL
     // Transitions to:
     //   IN_PROGRESS_INTERNAL  Once a server response is received from a
     //                         resumption.
     //   INTERRUPTED_INTERNAL  If the resumption request fails.
     //   CANCELLED_INTERNAL    On cancel.
     RESUMING_INTERNAL,
 
+    // The user removed this download from history but can undo this action.
+    // Transitions from:
+    //   CANCELLED_INTERNAL
+    //   COMPLETE_INTERNAL
+    //   INTERRUPTED_INTERNAL
+    // Transitions to:
+    //   CANCELLED_INTERNAL
+    //   COMPLETE_INTERNAL
+    //   INTERRUPTED_INTERNAL

[arv (Not doing code reviews), 2014/11/13 19:02:30]

This comment is confusing.

+    REMOVED_INTERNAL,
+
     MAX_DOWNLOAD_INTERNAL_STATE,
   };
 
   // Used with TransitionTo() to indicate whether or not to call
   // UpdateObservers() after the state transition.
   enum ShouldUpdateObservers {
     UPDATE_OBSERVERS,
     DONT_UPDATE_OBSERVERS
   };
 
@@ skipping 188 matching lines @@
 
   // Last reason.
   DownloadInterruptReason last_reason_;
 
   // Start time for recording statistics.
   base::TimeTicks start_tick_;
 
   // The current state of this download.
   DownloadInternalState state_;
 
+  // The previous state of this download (set in TransitionTo()).
+  DownloadInternalState prev_state_;
+
   // Current danger type for the download.
   DownloadDangerType danger_type_;
 
   // The views of this item in the download shelf and download contents.
   ObserverList<Observer> observers_;
 
   // Time the download was started.
   base::Time start_time_;
 
   // Time the download completed.
@@ skipping 49 matching lines @@
   const net::BoundNetLog bound_net_log_;
 
   base::WeakPtrFactory<DownloadItemImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItemImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_H_