Convert zoom callbacks to use CallbackRegistry

chrome/browser/ui/gtk/browser_toolbar_gtk.h

 // Copyright (c) 2012 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_UI_GTK_BROWSER_TOOLBAR_GTK_H_
 #define CHROME_BROWSER_UI_GTK_BROWSER_TOOLBAR_GTK_H_
 
 #include <gtk/gtk.h>
 #include <string>
 
@@ skipping 191 matching lines @@
   Browser* browser_;
   BrowserWindowGtk* window_;
 
   // Controls whether or not a home button should be shown on the toolbar.
   BooleanPrefMember show_home_button_;
 
   // Preferences controlling the configured home page.
   StringPrefMember home_page_;
   BooleanPrefMember home_page_is_new_tab_page_;
 
-  content::HostZoomMap::ZoomLevelChangedCallback zoom_callback_;
+  scoped_ptr<content::HostZoomMap::Subscription> zoom_subscription_;
   content::NotificationRegistrar registrar_;
 
   // A GtkEntry that isn't part of the hierarchy. We keep this for native
   // rendering.
   ui::OwnedWidgetGtk offscreen_entry_;
 
   // Manages the home button drop signal handler.
   scoped_ptr<ui::GtkSignalRegistrar> drop_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserToolbarGtk);
 };
 
 #endif  // CHROME_BROWSER_UI_GTK_BROWSER_TOOLBAR_GTK_H_