Virtual destructors should have virtual keyword.

chrome/browser/printing/print_job_worker.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 CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H__
 #define CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H__
 #pragma once
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 14 matching lines @@
 
 // Worker thread code. All this code, except for the constructor, is executed in
 // the worker thread. It manages the PrintingContext, which can be blocking
 // and/or run a message loop. This is the object that generates most
 // NOTIFY_PRINT_JOB_EVENT notifications, but they are generated through a
 // NotificationTask task to be executed from the right thread, the UI thread.
 // PrintJob always outlives its worker instance.
 class PrintJobWorker : public base::Thread {
  public:
   explicit PrintJobWorker(PrintJobWorkerOwner* owner);
-  ~PrintJobWorker();
+  virtual ~PrintJobWorker();
 
   void SetNewOwner(PrintJobWorkerOwner* new_owner);
 
   // Initializes the print settings. If |ask_user_for_settings| is true, a
   // Print... dialog box will be shown to ask the user his preference.
   void GetSettings(bool ask_user_for_settings,
                    gfx::NativeView parent_view,
                    int document_page_count,
                    bool has_selection,
                    bool use_overlays);
@@ skipping 84 matching lines @@
 
 template <>
 struct RunnableMethodTraits<printing::PrintJobWorker> {
   void RetainCallee(printing::PrintJobWorker* obj);
   void ReleaseCallee(printing::PrintJobWorker* obj);
  private:
   scoped_refptr<printing::PrintJobWorkerOwner> owner_;
 };
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H__