fix build issue on Linux with GCC 4.1.2...

webkit/port/platform/WidgetClientWin.h

 // Copyright (c) 2006-2008 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 WidgetClientWin_H__
 #define WidgetClientWin_H__
 
 #include "base/gfx/native_widget_types.h"
 #include "WidgetClient.h"
 
 class SkBitmap;
 
 namespace WebCore {
 
 class Cursor;
 class IntRect;
 class Range;
 
 // Generic interface for features needed by the Widget.
 class WidgetClientWin : public WidgetClient {
 public:
+    virtual ~WidgetClientWin() {}
+    
     // Returns the containing window for the Widget.
     // TODO(pinkerton): this needs a better name, "window" is incorrect on other
     // platforms.
     virtual gfx::ViewHandle containingWindow() = 0;
 
     // Invalidate a region of the widget's containing window.
     virtual void invalidateRect(const IntRect& damagedRect) = 0;
 
     // Scroll the region of the widget's containing window within the given
     // clipRect by the specified dx and dy.
@@ skipping 30 matching lines @@
     // frame does not have an active tickmark (for example if the active
     // tickmark resides in another frame) this function returns kNoTickmark.
     static const size_t kNoTickmark = -1;
     virtual size_t getActiveTickmarkIndex(WebCore::Frame* frame) = 0;
 };
 
 } // namespace WebCore
 
 #endif  // WidgetClientWin_H__