Adds the UserInputMonitor implementation for Windows.

media/base/keyboard_event_counter.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_KEYBOARD_EVENT_COUNTER_H_
 #define MEDIA_BASE_KEYBOARD_EVENT_COUNTER_H_
 
 #include <set>
 
 #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"
 
 namespace media {
 
 // This class tracks the total number of keypresses based on the OnKeyboardEvent
 // calls it receives from the client.
 // Multiple key down events for the same key are counted as one keypress until
 // the same key is released.
-class KeyboardEventCounter {
+class MEDIA_EXPORT KeyboardEventCounter {
  public:
   KeyboardEventCounter();
   ~KeyboardEventCounter();
 
   // Resets the count to 0. Must be called on the same thread as
   // OnKeyboardEvent.
   void Reset();
 
   // Returns the total number of keypresses since its creation or last Reset()
   // call. Can be called on any thread.
   size_t GetKeyPressCount() const;
 
   // The client should call this method on key down or key up events.
   // Must be called on a single thread.
   void OnKeyboardEvent(ui::EventType event, ui::KeyboardCode key_code);
 
  private:
   // The set of keys currently held down.
   std::set<ui::KeyboardCode> pressed_keys_;
 
   size_t total_key_presses_;
 
   DISALLOW_COPY_AND_ASSIGN(KeyboardEventCounter);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_KEYBOARD_EVENT_COUNTER_H_