Virtual destructors should have virtual keyword.

printing/printing_context_mac.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_MAC_H_
 #define PRINTING_PRINTING_CONTEXT_MAC_H_
 
 #include <string>
 
 #include "base/memory/scoped_nsobject.h"
 #include "printing/printing_context.h"
 #include "printing/print_job_constants.h"
 
 #ifdef __OBJC__
 @class NSPrintInfo;
 #else
 class NSPrintInfo;
 #endif  // __OBJC__
 
 namespace printing {
 
 class PrintingContextMac : public PrintingContext {
  public:
   explicit PrintingContextMac(const std::string& app_locale);
-  ~PrintingContextMac();
+  virtual ~PrintingContextMac();
 
   // PrintingContext implementation.
   virtual void AskUserForSettings(gfx::NativeView parent_view,
                                   int max_pages,
                                   bool has_selection,
                                   PrintSettingsCallback* callback);
   virtual Result UseDefaultSettings();
   virtual Result UpdatePrintSettings(const DictionaryValue& job_settings,
                                      const PageRanges& ranges);
   virtual Result InitWithSettings(const PrintSettings& settings);
@@ skipping 42 matching lines @@
   // The current page's context; only valid between NewPage and PageDone call
   // pairs.
   CGContext* context_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintingContextMac);
 };
 
 }  // namespace printing
 
 #endif  // PRINTING_PRINTING_CONTEXT_MAC_H_