Create TetherService, a TetherAllowed pref, and use DependencyManager for RegisterProfilePrefs call…

chrome/browser/tether/tether_service_factory.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 CHROME_BROWSER_TETHER_TETHER_SERVICE_FACTORY_H_
+#define CHROME_BROWSER_TETHER_TETHER_SERVICE_FACTORY_H_
+
+#include "base/macros.h"
+#include "chrome/browser/tether/tether_service.h"
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+
+namespace content {
+class BrowserContext;
+}
+
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}
+
+// Singleton factory that builds and owns all TetherServices.
+class TetherServiceFactory : public BrowserContextKeyedServiceFactory {
+ public:
+  static TetherServiceFactory* GetInstance();
+
+  static TetherService* GetForBrowserContext(
+      content::BrowserContext* browser_context);
+
+ private:
+  friend struct base::DefaultSingletonTraits<TetherServiceFactory>;
+
+  TetherServiceFactory();
+  ~TetherServiceFactory() override;
+
+  // BrowserContextKeyedServiceFactory:
+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+  void RegisterProfilePrefs(
+      user_prefs::PrefRegistrySyncable* registry) override;
+
+  DISALLOW_COPY_AND_ASSIGN(TetherServiceFactory);
+};
+
+#endif  // CHROME_BROWSER_TETHER_TETHER_SERVICE_FACTORY_H_