GTK: make more use of gtk_signal convenience macros/signal registrar.

chrome/browser/gtk/tab_contents_drag_source.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_GTK_TAB_CONTENTS_DRAG_SOURCE_H_
 #define CHROME_BROWSER_GTK_TAB_CONTENTS_DRAG_SOURCE_H_
 
 #include <gtk/gtk.h>
 
 #include "app/gtk_signal.h"
@@ skipping 72 matching lines @@
 
   // The file mime type for a drag-out download.
   string16 wide_download_mime_type_;
 
   // The file name to be saved to for a drag-out download.
   FilePath download_file_name_;
 
   // The URL to download from for a drag-out download.
   GURL download_url_;
 
-  // The widget that provides visual feedback for the drag. We use this instead
-  // of gtk_drag_set_icon_pixbuf() because some window managers will use shadows
-  // or other visual effects on top level windows.
+  // The widget that provides visual feedback for the drag.
   GtkWidget* drag_icon_;
 
+  GtkSignalRegistrar signals_;
+
   DISALLOW_COPY_AND_ASSIGN(TabContentsDragSource);
 };
 
 #endif  // CHROME_BROWSER_GTK_TAB_CONTENTS_DRAG_SOURCE_H_