Fix DeviceStatusCollectorTest.MaxStoredPeriods.

base/test/scoped_environment_variable.h

+// 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 BASE_TEST_SCOPED_ENVIRONMENT_VARIABLE_H_
+#define BASE_TEST_SCOPED_ENVIRONMENT_VARIABLE_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace base {
+
+class Environment;
+
+// Overrides the environment variable value for |name| while in scope. The
+// previous value is restored when this goes out of scope.
+class ScopedEnvironmentVariable {
+ public:
+  ScopedEnvironmentVariable(const std::string& name, const std::string& value);
+  ~ScopedEnvironmentVariable();
+
+ private:
+  std::string name_;
+  bool prev_was_set_;
+  std::string prev_value_;
+  scoped_ptr<base::Environment> environment_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedEnvironmentVariable);
+};
+
+}  // namespace base
+
+#endif  // BASE_TEST_SCOPED_ENVIRONMENT_VARIABLE_H_