Adds the UserInputMonitor implementation for Mac.

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 <set>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/synchronization/lock.h"
 #include "media/base/media_export.h"
 #include "ui/base/events/event_constants.h"
 #include "ui/base/keycodes/keyboard_codes.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 deleted object.
 class MEDIA_EXPORT 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() {}
@@ skipping 41 matching lines @@
   virtual void StartKeyboardMonitoring() = 0;
   virtual void StopKeyboardMonitoring() = 0;
 
   base::Lock lock_;
   ObserverList<MouseEventListener, true> mouse_listeners_;
   ObserverList<KeyStrokeListener, true> key_stroke_listeners_;
   bool monitoring_mouse_;
   bool monitoring_keyboard_;
   // The set of keys currently held down. Used for convering raw keyboard events
   // into KeyStrokeListener callbacks.
-  std::set<ui::KeyboardCode> pressed_keys_;
+  std::set<int> pressed_keys_;
 
   DISALLOW_COPY_AND_ASSIGN(UserInputMonitor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_USER_INPUT_MONITOR_H_