Reland DownloadItem::Observer::OnDownloadDestroyed() replaces DownloadItem::REMOVING

content/public/browser/download_item.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.
 //
 // Each download is represented by a DownloadItem, and all DownloadItems
 // are owned by the DownloadManager which maintains a global list of all
 // downloads. DownloadItems are created when a user initiates a download,
 // and exist for the duration of the browser life time.
 //
 // Download observers:
@@ skipping 44 matching lines @@
   enum DownloadState {
     // Download is actively progressing.
     IN_PROGRESS = 0,
 
     // Download is completely finished.
     COMPLETE,
 
     // Download has been cancelled.
     CANCELLED,
 
-    // This state indicates that the download item is about to be destroyed,
-    // and observers seeing this state should release all references.
-    REMOVING,
-
     // This state indicates that the download has been interrupted.
     INTERRUPTED,
 
     // Maximum value.
     MAX_DOWNLOAD_STATE
   };
 
   enum SafetyState {
     SAFE = 0,
     DANGEROUS,
@@ skipping 17 matching lines @@
   // A fake download table ID which represents a download that has started,
   // but is not yet in the table.
   static const int kUninitializedHandle;
 
   static const char kEmptyFileHash[];
 
   // Interface that observers of a particular download must implement in order
   // to receive updates to the download's status.
   class CONTENT_EXPORT Observer {
    public:
-    virtual void OnDownloadUpdated(DownloadItem* download) = 0;
+    virtual void OnDownloadUpdated(DownloadItem* download) {}
 
     // Called when a downloaded file has been opened.
-    virtual void OnDownloadOpened(DownloadItem* download) = 0;
+    virtual void OnDownloadOpened(DownloadItem* download) {}
+
+    // Called when the user removes a download.
+    virtual void OnDownloadRemoved(DownloadItem* download) {}
+
+    // Called when the download is being destroyed. This happens after
+    // every OnDownloadRemoved() as well as when the DownloadManager is going
+    // down.
+    virtual void OnDownloadDestroyed(DownloadItem* download) {}
 
    protected:
     virtual ~Observer() {}
   };
 
   virtual ~DownloadItem() {}
 
   virtual void AddObserver(DownloadItem::Observer* observer) = 0;
   virtual void RemoveObserver(DownloadItem::Observer* observer) = 0;
 
@@ skipping 166 matching lines @@
   virtual FilePath GetUserVerifiedFilePath() const = 0;
 
   virtual std::string DebugString(bool verbose) const = 0;
 
   virtual void MockDownloadOpenForTesting() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_DOWNLOAD_ITEM_H_