Add a mojo::test::ScopedTestDir and convert tests to use it.

mojo/edk/test/scoped_test_dir.h

+// Copyright 2015 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 MOJO_EDK_TEST_SCOPED_TEST_DIR_H_
+#define MOJO_EDK_TEST_SCOPED_TEST_DIR_H_
+
+#include "base/files/scoped_temp_dir.h"
+#include "mojo/edk/util/scoped_file.h"
+#include "mojo/public/cpp/system/macros.h"
+
+namespace mojo {
+namespace test {
+
+// Creates/destroyes a temporary directory for test purposes. (Unlike
+// |base::ScopedTempDir|, this automatically creates the temporary directory.)
+class ScopedTestDir {
+ public:
+  ScopedTestDir();
+  ~ScopedTestDir();
+
+  util::ScopedFILE CreateFile();
+
+ private:
+  base::ScopedTempDir temp_dir_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(ScopedTestDir);
+};
+
+}  // namespace test
+}  // namespace mojo
+
+#endif  // MOJO_EDK_TEST_SCOPED_TEST_DIR_H_