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/observer_list_threadsafe.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.
+// Thread safe. The listeners are called on the thread where the listeners are
+// added.
 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() {}
   };
+  typedef ObserverListThreadSafe<UserInputMonitor::MouseEventListener>
+      MouseListenerList;
 
   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(
       const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner,
       const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner);
@@ skipping 11 matching lines @@
 
   // 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:
-  // Called by the platform-specific sub-classes to propagate the events to the
-  // listeners.
-  void OnMouseEvent(const SkIPoint& position);
+  scoped_refptr<MouseListenerList> mouse_listeners() {
+    return mouse_listeners_;
+  }
 
  private:
+  virtual void StartKeyboardMonitoring() = 0;
+  virtual void StopKeyboardMonitoring() = 0;
   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_;
+  size_t mouse_listeners_count_;

[Wez, 2013/09/13 10:01:27]

nit: Name these two counters consistently, e.g. mouse_monitor_count_,
keyboard_monitor_count_

+  scoped_refptr<MouseListenerList> mouse_listeners_;
 
   DISALLOW_COPY_AND_ASSIGN(UserInputMonitor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_USER_INPUT_MONITOR_H_