Revert 149794 - DownloadItem::Observer::OnDownloadDestroyed() replaces DownloadItem::REMOVING

content/public/browser/download_item.h

Index: content/public/browser/download_item.h
===================================================================
--- content/public/browser/download_item.h	(revision 150095)
+++ content/public/browser/download_item.h	(working copy)
@@ -61,6 +61,10 @@
     // 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,
 
@@ -98,19 +102,11 @@
   // to receive updates to the download's status.
   class CONTENT_EXPORT Observer {
    public:
-    virtual void OnDownloadUpdated(DownloadItem* download) {}
+    virtual void OnDownloadUpdated(DownloadItem* download) = 0;
 
     // Called when a downloaded file has been opened.
-    virtual void OnDownloadOpened(DownloadItem* download) {}
+    virtual void OnDownloadOpened(DownloadItem* download) = 0;
 
-    // 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() {}
   };