Adds the UserInputMonitor implementation for Windows.

media/base/user_input_monitor.h

 // Copyright 2013 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 MEDIA_BASE_USER_INPUT_MONITOR_H_
 #define MEDIA_BASE_USER_INPUT_MONITOR_H_
 
+#include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/synchronization/lock.h"
 #include "media/base/media_export.h"
 
 struct SkIPoint;
 
 namespace base {
 class SingleThreadTaskRunner;
 }  // namespace base
 
 namespace media {
 
 // Monitors and notifies about mouse movements and keyboard events.
 // Thread safe. The thread on which the listenters are called is not guaranteed.
 // The callers should not perform expensive/blocking tasks in the callback since
 // it might be called on the browser UI/IO threads.
 // The object must outlive the browser UI/IO threads to make sure the callbacks
 // will not access a deleted object.
-class MEDIA_EXPORT UserInputMonitor {
+class MEDIA_EXPORT UserInputMonitor
+   : public base::RefCountedThreadSafe<UserInputMonitor> {
  public:
   // The interface to receive mouse movement events.
   class MEDIA_EXPORT MouseEventListener {
    public:
     // |position| is the new mouse position.
     virtual void OnMouseMoved(const SkIPoint& position) = 0;
 
    protected:
     virtual ~MouseEventListener() {}
   };
 
   UserInputMonitor();
-  virtual ~UserInputMonitor();
 
   // Creates a platform-specific instance of UserInputMonitor.
   // |io_task_runner| is the task runner for an IO thread.
   // |ui_task_runner| is the task runner for a UI thread.
-  static scoped_ptr<UserInputMonitor> Create(
+  static scoped_refptr<UserInputMonitor> Create(
       const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner,
       const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner);
 
   // The same |listener| should only be added once.
   // The clients should make sure to call Remove*Listener before |listener| is
   // destroyed.
   void AddMouseListener(MouseEventListener* listener);
   void RemoveMouseListener(MouseEventListener* listener);
 
   // A caller must call EnableKeyPressMonitoring and
   // DisableKeyPressMonitoring in pair.
   void EnableKeyPressMonitoring();
   void DisableKeyPressMonitoring();
 
   // Returns the number of keypresses. The starting point from when it is
   // counted is not guaranteed, but consistent within the pair of calls of
   // EnableKeyPressMonitoring and DisableKeyPressMonitoring. So a caller can
   // use the difference between the values returned at two times to get the
   // number of keypresses happened within that time period, but should not make
   // any assumption on the initial value.
   virtual size_t GetKeyPressCount() const = 0;
 
  protected:
+  friend class base::RefCountedThreadSafe<UserInputMonitor>;
+  virtual ~UserInputMonitor();
+
   // Called by the platform-specific sub-classes to propagate the events to the
   // listeners.
   void OnMouseEvent(const SkIPoint& position);
 
  private:
   virtual void StartMouseMonitoring() = 0;
   virtual void StopMouseMonitoring() = 0;
   virtual void StartKeyboardMonitoring() = 0;
   virtual void StopKeyboardMonitoring() = 0;
 
   base::Lock lock_;
   ObserverList<MouseEventListener, true> mouse_listeners_;
   bool monitoring_mouse_;
   size_t key_press_counter_references_;
 
   DISALLOW_COPY_AND_ASSIGN(UserInputMonitor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_USER_INPUT_MONITOR_H_