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

chrome/browser/download/download_completion_observer_win.cc

Index: chrome/browser/download/download_completion_observer_win.cc
diff --git a/chrome/browser/download/download_completion_observer_win.cc b/chrome/browser/download/download_completion_observer_win.cc
index 5a009e77ed6c30576dfeb8876c9c75f4fc186b06..809e896a957830ac0f8fd9b368877e5aa7cd5bb0 100644
--- a/chrome/browser/download/download_completion_observer_win.cc
+++ b/chrome/browser/download/download_completion_observer_win.cc
@@ -83,7 +83,6 @@ void DownloadCompletionObserver::OnDownloadUpdated(DownloadItem* download) {
       break;
     }
 
-    case DownloadItem::REMOVING:
     case DownloadItem::INTERRUPTED:
     case DownloadItem::CANCELLED: {
       DCHECK(ContainsKey(download_items_, download));
@@ -97,6 +96,12 @@ void DownloadCompletionObserver::OnDownloadUpdated(DownloadItem* download) {
   }
 }
 
+void DownloadCompletionObserver::OnDownloadDestroyed(DownloadItem* download) {
+  DCHECK(ContainsKey(download_items_, download));
+  download_items_.erase(download);
+  download->RemoveObserver(this);
+}
+
 void DownloadCompletionObserver::ClearDownloadItems() {
   for (std::set<DownloadItem*>::iterator it = download_items_.begin();
        it != download_items_.end(); ++it) {