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

content/public/browser/download_item.h

Index: content/public/browser/download_item.h
diff --git a/content/public/browser/download_item.h b/content/public/browser/download_item.h
index c440bcedc45a2643df7ebb5292b5dee982e0e4b9..26e5565639dad2d985a0a49e81790c4ab031f7f2 100644
--- a/content/public/browser/download_item.h
+++ b/content/public/browser/download_item.h
@@ -62,10 +62,6 @@ class CONTENT_EXPORT DownloadItem : public base::SupportsUserData {
     // 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,
 
@@ -103,10 +99,18 @@ class CONTENT_EXPORT DownloadItem : public base::SupportsUserData {
   // 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() {}