Virtual destructors should have virtual keyword.

printing/printing_context_cairo.h

 // Copyright (c) 2011 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 PRINTING_PRINTING_CONTEXT_CAIRO_H_
 #define PRINTING_PRINTING_CONTEXT_CAIRO_H_
 
 #include <string>
 
 #include "printing/printing_context.h"
 
 namespace printing {
 
 class Metafile;
 class PrintDialogGtkInterface;
 
 class PrintingContextCairo : public PrintingContext {
  public:
   explicit PrintingContextCairo(const std::string& app_locale);
-  ~PrintingContextCairo();
+  virtual ~PrintingContextCairo();
 
 #if !defined(OS_CHROMEOS)
   // Sets the function that creates the print dialog.
   static void SetCreatePrintDialogFunction(
       PrintDialogGtkInterface* (*create_dialog_func)(
           PrintingContextCairo* context));
 
   // Prints the document contained in |metafile|.
   void PrintDocument(const Metafile* metafile);
 #endif
@@ skipping 20 matching lines @@
   string16 document_name_;
   PrintDialogGtkInterface* print_dialog_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PrintingContextCairo);
 };
 
 }  // namespace printing
 
 #endif  // PRINTING_PRINTING_CONTEXT_CAIRO_H_