Add the "virtual" keyword on method overrides that are missing it.

chrome/browser/gtk/collected_cookies_gtk.h

 // Copyright (c) 2010 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.
 
 // This is the Gtk implementation of the collected Cookies dialog.
 
 #ifndef CHROME_BROWSER_GTK_COLLECTED_COOKIES_GTK_H_
 #define CHROME_BROWSER_GTK_COLLECTED_COOKIES_GTK_H_
 #pragma once
 
@@ skipping 35 matching lines @@
 
   // Enable the allow/block buttons if at least one origin node is selected.
   void EnableControls();
 
   // Add exceptions for all origin nodes within the selection.
   void AddExceptions(GtkTreeSelection* selection,
                      gtk_tree::TreeAdapter* adapter,
                      ContentSetting setting);
 
   // Notification Observer implementation.
-  void Observe(NotificationType type,
-               const NotificationSource& source,
-               const NotificationDetails& details);
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
 
   // Callbacks.
   CHROMEGTK_CALLBACK_2(CollectedCookiesGtk, void, OnTreeViewRowExpanded,
                        GtkTreeIter*, GtkTreePath*);
   CHROMEGTK_CALLBACK_0(CollectedCookiesGtk, void, OnTreeViewSelectionChange);
   CHROMEGTK_CALLBACK_0(CollectedCookiesGtk, void, OnClose);
   CHROMEGTK_CALLBACK_0(CollectedCookiesGtk, void, OnBlockAllowedButtonClicked);
   CHROMEGTK_CALLBACK_0(CollectedCookiesGtk, void, OnAllowBlockedButtonClicked);
   CHROMEGTK_CALLBACK_0(CollectedCookiesGtk, void,
                        OnForSessionBlockedButtonClicked);
@@ skipping 30 matching lines @@
   // The Cookies Table model.
   scoped_ptr<CookiesTreeModel> allowed_cookies_tree_model_;
   scoped_ptr<CookiesTreeModel> blocked_cookies_tree_model_;
   scoped_ptr<gtk_tree::TreeAdapter> allowed_cookies_tree_adapter_;
   scoped_ptr<gtk_tree::TreeAdapter> blocked_cookies_tree_adapter_;
 
   DISALLOW_COPY_AND_ASSIGN(CollectedCookiesGtk);
 };
 
 #endif  // CHROME_BROWSER_GTK_COLLECTED_COOKIES_GTK_H_