Virtual destructors should have virtual keyword.

base/task_queue.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 BASE_TASK_QUEUE_H_
 #define BASE_TASK_QUEUE_H_
 #pragma once
 
 #include <deque>
 
 #include "base/base_api.h"
 #include "base/task.h"
 
 // A TaskQueue is a queue of tasks waiting to be run.  To run the tasks, call
 // the Run method.  A task queue is itself a Task so that it can be placed in a
 // message loop or another task queue.
 class BASE_API TaskQueue : public Task {
  public:
   TaskQueue();
-  ~TaskQueue();
+  virtual ~TaskQueue();
 
   // Push the specified task onto the queue.  When the queue is run, the tasks
   // will be run in the order they are pushed.
   //
   // This method takes ownership of |task| and will delete task after it is run
   // (or when the TaskQueue is destroyed, if we never got a chance to run it).
   void Push(Task* task);
 
   // Remove all tasks from the queue.  The tasks are deleted.
   void Clear();
 
   // Returns true if this queue contains no tasks.
   bool IsEmpty() const;
 
   // Run all the tasks in the queue.  New tasks pushed onto the queue during
   // a run will be run next time |Run| is called.
   virtual void Run();
 
  private:
    // The list of tasks we are waiting to run.
    std::deque<Task*> queue_;
 };
 
 #endif  // BASE_TASK_QUEUE_H_