Add Browser class to controll when the application should quit.

browser/browser_mac.mm

@@ -0,0 +1,15 @@
+// Copyright (c) 2013 GitHub, Inc. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "browser/browser.h"
+
+#import "browser/atom_application_mac.h"
+
+namespace atom {
+
+void Browser::Terminate() {
+  [[AtomApplication sharedApplication] terminate:nil];
+}
+
+}  // namespace atom