Add ManagedUserSettingsService and a SupervisedUserPrefStore using it.

chrome/browser/managed_mode/managed_user_settings_service.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_settings_service.h"
+
+#include "base/callback.h"
+#include "base/logging.h"
+
+void ManagedUserSettingsService::Subscribe(const SettingsCallback& callback) {
+  if (IsReady()) {
+    scoped_ptr<base::DictionaryValue> settings = GetSettingsIfActive();
+    callback.Run(settings.get());
+  }
+
+  subscribers_.push_back(callback);
+}
+
+void ManagedUserSettingsService::Activate() {
+  active_ = true;
+  NotifySettingsChanged();
+}
+
+ManagedUserSettingsService::ManagedUserSettingsService() : active_(false) {}
+ManagedUserSettingsService::~ManagedUserSettingsService() {}
+
+scoped_ptr<base::DictionaryValue>
+ManagedUserSettingsService::GetSettingsIfActive() {
+  DCHECK(IsReady());
+  if (!active_)
+    return scoped_ptr<base::DictionaryValue>();
+
+  return GetSettings();
+}
+
+void ManagedUserSettingsService::NotifySettingsChanged() {
+  if (!IsReady())
+    return;
+
+  scoped_ptr<base::DictionaryValue> settings = GetSettingsIfActive();
+  for (std::vector<SettingsCallback>::iterator it = subscribers_.begin();
+       it != subscribers_.end(); ++it) {
+    it->Run(settings.get());
+  }
+}