[iOS] Add FakeSyncService and factory for testing

ios/public/test/fake_sync_service_factory.h

+// Copyright 2015 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_PUBLIC_TEST_FAKE_SYNC_SERVICE_FACTORY_H_
+#define IOS_PUBLIC_TEST_FAKE_SYNC_SERVICE_FACTORY_H_
+
+#include "base/macros.h"
+#include "base/memory/singleton.h"
+#include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
+
+namespace sync_driver {
+class FakeSyncService;
+}
+
+namespace ios {
+
+class FakeSyncServiceFactory : public BrowserStateKeyedServiceFactory {
+ public:
+  // Returns the singleton FakeSyncServiceFactory instance.
+  static FakeSyncServiceFactory* GetInstance();
+
+  // Returns the FakeSyncService associated to |browser_state|.
+  static sync_driver::FakeSyncService* GetForBrowserState(
+      web::BrowserState* browser_state);
+
+ private:
+  friend struct DefaultSingletonTraits<FakeSyncServiceFactory>;
+
+  // BrowserStateKeyedServiceFactory implementation:
+  KeyedService* BuildServiceInstanceFor(
+      web::BrowserState* context) const override;
+
+  FakeSyncServiceFactory();
+  ~FakeSyncServiceFactory() override;
+
+  DISALLOW_COPY_AND_ASSIGN(FakeSyncServiceFactory);
+};
+
+}  // namespace ios
+
+#endif  // IOS_PUBLIC_TEST_FAKE_SYNC_SERVICE_FACTORY_H_