MacViews: Create abstraction for event monitoring

ui/views/event_monitor_mac.h

+// Copyright 2014 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 UI_VIEWS_EVENT_MONITOR_MAC_H_
+#define UI_VIEWS_EVENT_MONITOR_MAC_H_
+
+#include "base/macros.h"
+#include "ui/views/event_monitor.h"
+
+#import <Cocoa/Cocoa.h>
+
+namespace views {
+
+class EventMonitorMac : public EventMonitor {
+ public:
+  explicit EventMonitorMac(ui::EventHandler* event_handler);
+  virtual ~EventMonitorMac();
+
+ private:
+  id monitor_;
+
+  DISALLOW_COPY_AND_ASSIGN(EventMonitorMac);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_EVENT_MONITOR_MAC_H_