Don't allow multiple opens for Pepper FileSystem.

ppapi/tests/test_file_system.h

+// Copyright (c) 2011 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 PAPPI_TESTS_TEST_FILE_SYSTEM_H_
+#define PAPPI_TESTS_TEST_FILE_SYSTEM_H_
+
+#include <string>
+
+#include "ppapi/tests/test_case.h"
+
+class TestFileSystem : public TestCase {
+ public:
+  explicit TestFileSystem(TestingInstance* instance) : TestCase(instance) {}
+
+  // TestCase implementation.
+  virtual bool Init();
+  virtual void RunTest();
+
+ private:
+  std::string TestOpen();
+  std::string TestMultipleOpens();
+};
+
+#endif  // PAPPI_TESTS_TEST_FILE_SYSTEM_H_
+