Make the UI an observer of downloads.

chrome/browser/download/download_service.h

Index: chrome/browser/download/download_service.h
diff --git a/chrome/browser/download/download_service.h b/chrome/browser/download/download_service.h
index 601b3edcafb9b4a13d8352fae29a45aeeb273f39..742d576a976158cf19c3891bbc0ca0e8286fea16 100644
--- a/chrome/browser/download/download_service.h
+++ b/chrome/browser/download/download_service.h
@@ -15,6 +15,7 @@
 
 class ChromeDownloadManagerDelegate;
 class DownloadHistory;
+class DownloadUIController;
 class ExtensionDownloadsEventRouter;
 class Profile;
 
@@ -72,6 +73,11 @@ class DownloadService : public ProfileKeyedService {
 
   scoped_ptr<DownloadHistory> download_history_;
 
+  // The UI controller is responsible for observing the download manager and
+  // notifying the UI of any new downloads. Its lifetime matches that of the
+  // associated download manager.
+  scoped_ptr<DownloadUIController> download_ui_;
+
   // On Android, GET downloads are not handled by the DownloadManager.
   // Once we have extensions on android, we probably need the EventRouter
   // in ContentViewDownloadDelegate which knows about both GET and POST