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

webkit/glue/plugins/pepper_scrollbar.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.
 
 #ifndef WEBKIT_GLUE_PLUGINS_PEPPER_SCROLLBAR_H_
 #define WEBKIT_GLUE_PLUGINS_PEPPER_SCROLLBAR_H_
 
 #include <vector>
 
 #include "gfx/rect.h"
 #include "ppapi/c/dev/ppb_scrollbar_dev.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebRect.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebScrollbarClient.h"
 #include "webkit/glue/plugins/pepper_widget.h"
 
 namespace pepper {
 
 class PluginInstance;
 
 class Scrollbar : public Widget, public WebKit::WebScrollbarClient {
  public:
   Scrollbar(PluginInstance* instance, bool vertical);
   virtual ~Scrollbar();
 
   // Returns a pointer to the interface implementing PPB_Scrollbar that is
   // exposed to the plugin.
   static const PPB_Scrollbar_Dev* GetInterface();
 
   // Resource overrides.
-  Scrollbar* AsScrollbar() { return this; }
+  virtual Scrollbar* AsScrollbar();
 
   // PPB_Scrollbar implementation.
   uint32_t GetValue();
   void SetValue(uint32_t value);
   void SetDocumentSize(uint32_t size);
   void SetTickMarks(const PP_Rect* tick_marks, uint32_t count);
   void ScrollBy(PP_ScrollBy_Dev unit, int32_t multiplier);
 
   // PPB_Widget implementation.
   virtual bool Paint(const PP_Rect* rect, ImageData* image);
@@ skipping 12 matching lines @@
   void NotifyInvalidate();
 
   gfx::Rect dirty_;
   std::vector<WebKit::WebRect> tickmarks_;
   scoped_ptr<WebKit::WebScrollbar> scrollbar_;
 };
 
 }  // namespace pepper
 
 #endif  // WEBKIT_GLUE_PLUGINS_PEPPER_SCROLLBAR_H_