Add ManagedUserSettingsService and a SupervisedUserPrefStore using it.

chrome/browser/managed_mode/managed_user_constants.cc

+// Copyright 2013 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.
+
+#include "chrome/browser/managed_mode/managed_user_constants.h"
+
+namespace managed_users {
+
+const char kContentPackDefaultFilteringBehavior[] =
+    "ContentPackDefaultFilteringBehavior";
+const char kContentPackManualBehaviorHosts[] = "ContentPackManualBehaviorHosts";
+const char kContentPackManualBehaviorURLs[] = "ContentPackManualBehaviorURLs";
+const char kForceSafeSearch[] = "ForceSafeSearch";
+const char kSigninAllowed[] = "SigninAllowed";
+const char kUserName[] = "UserName";
+
+}  // namespace managed_users