[iOS] Add FakeSyncService and factory for testing

ios/public/test/test_keyed_service_provider.cc

+// 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.
+
+#include "ios/public/test/test_keyed_service_provider.h"
+
+#include "components/sync_driver/fake_sync_service.h"
+#include "ios/public/provider/chrome/browser/browser_state/chrome_browser_state.h"
+#include "ios/public/test/fake_sync_service_factory.h"
+
+namespace ios {
+
+TestKeyedServiceProvider::TestKeyedServiceProvider() {
+}
+
+TestKeyedServiceProvider::~TestKeyedServiceProvider() {
+}
+
+KeyedServiceBaseFactory* TestKeyedServiceProvider::GetSyncServiceFactory() {
+  return FakeSyncServiceFactory::GetInstance();
+}
+
+sync_driver::SyncService*
+TestKeyedServiceProvider::GetSyncServiceForBrowserState(
+    ChromeBrowserState* browser_state) {
+  return FakeSyncServiceFactory::GetForBrowserState(browser_state);
+}
+
+}  // namespace ios