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

chrome/browser/gtk/status_bubble_gtk.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_STATUS_BUBBLE_GTK_H_
 #define CHROME_BROWSER_GTK_STATUS_BUBBLE_GTK_H_
 #pragma once
 
 #include <gtk/gtk.h>
 
@@ skipping 37 matching lines @@
   // AnimationDelegate implementation.
   virtual void AnimationEnded(const Animation* animation);
   virtual void AnimationProgressed(const Animation* animation);
 
   // Called when the download shelf becomes visible or invisible.
   // This is used by to ensure that the status bubble does not obscure
   // the download shelf, when it is visible.
   virtual void UpdateDownloadShelfVisibility(bool visible);
 
   // Overridden from NotificationObserver:
-  void Observe(NotificationType type,
-               const NotificationSource& source,
-               const NotificationDetails& details);
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
 
   // Top of the widget hierarchy for a StatusBubble. This top level widget is
   // guarenteed to have its gtk_widget_name set to "status-bubble" for
   // identification.
   GtkWidget* widget() { return container_.get(); }
 
  private:
   // Sets the text of the label widget and controls visibility. (As contrasted
   // with setting the current status or URL text, which may be ignored for now).
   void SetStatusTextTo(const std::string& status_utf8);
@@ skipping 86 matching lines @@
   bool download_shelf_is_visible_;
 
   // 'location' and 'left_content' values from the last invocation of
   // MouseMoved().  We hang onto these so we can move the bubble if necessary
   // when its text changes, triggering a size change.
   gfx::Point last_mouse_location_;
   bool last_mouse_left_content_;
 };
 
 #endif  // CHROME_BROWSER_GTK_STATUS_BUBBLE_GTK_H_