Remove DeleteTask and convert remaining users.

content/public/browser/download_manager.h

Index: content/public/browser/download_manager.h
diff --git a/content/public/browser/download_manager.h b/content/public/browser/download_manager.h
index c123cc05a6d3d61528c419a8fc4896558f7c98e8..e88b950013a15a041aec20bfdf8c5ee9a7dcdb7e 100644
--- a/content/public/browser/download_manager.h
+++ b/content/public/browser/download_manager.h
@@ -34,6 +34,7 @@
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
+#include "base/message_loop_helpers.h"
 #include "base/time.h"
 #include "content/browser/download/download_id.h"
 #include "content/browser/download/interrupt_reasons.h"
@@ -263,7 +264,7 @@ class CONTENT_EXPORT DownloadManager
       DownloadManager, content::BrowserThread::DeleteOnUIThread>;
   friend struct content::BrowserThread::DeleteOnThread<
       content::BrowserThread::UI>;
-  friend class DeleteTask<DownloadManager>;
+  friend class base::DeleteHelper<DownloadManager>;
 };
 
 }  // namespace content