TestScreen shouldn't be marked aura export

ash/shell_observer.h

Index: ash/shell_observer.h
diff --git a/ash/shell_observer.h b/ash/shell_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..0ecf92711896a893ae08c3566a2a23bf4bb20fb9
--- /dev/null
+++ b/ash/shell_observer.h
@@ -0,0 +1,24 @@
+// Copyright (c) 2012 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 ASH_SHELLOBSERVER_H_
+#define ASH_SHELLOBSERVER_H_
+#pragma once
+
+#include "ash/ash_export.h"
+
+namespace ash {
+
+class ASH_EXPORT ShellObserver {
+ public:
+  // Invoked after the screen's work area insets changes.
+  virtual void OnScreenWorkAreaInsetsChanged() {}
+
+ protected:
+  virtual ~ShellObserver() {}
+};
+
+}  // namespace ash
+
+#endif  // ASH_SHELLOBSERVER_H_