Simplify registration of a test ChromeBrowserStateManager.

ios/chrome/test/ios_chrome_scoped_testing_chrome_browser_state_manager.h

+// Copyright 2017 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 IOS_CHROME_TEST_IOS_CHROME_SCOPED_TESTING_CHROME_BROWSER_STATE_MANAGER_H_
+#define IOS_CHROME_TEST_IOS_CHROME_SCOPED_TESTING_CHROME_BROWSER_STATE_MANAGER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+
+namespace ios {
+class ChromeBrowserStateManager;
+}
+
+// Helper class to register an ios::ChromeBrowserStateManager against
+// the TestApplicationContext using local scoping to do proper cleanup.
+class IOSChromeScopedTestingChromeBrowserStateManager {
+ public:
+  explicit IOSChromeScopedTestingChromeBrowserStateManager(
+      std::unique_ptr<ios::ChromeBrowserStateManager> browser_state_manager);
+  ~IOSChromeScopedTestingChromeBrowserStateManager();
+
+ private:
+  std::unique_ptr<ios::ChromeBrowserStateManager> browser_state_manager_;
+  ios::ChromeBrowserStateManager* saved_browser_state_manager_;
+
+  DISALLOW_COPY_AND_ASSIGN(IOSChromeScopedTestingChromeBrowserStateManager);
+};
+
+#endif  // IOS_CHROME_TEST_IOS_CHROME_SCOPED_TESTING_CHROME_BROWSER_STATE_MANAGER_H_