Add Desktop iOS promotion logging to chrome ios app.

ios/chrome/browser/desktop_promotion/desktop_promotion_sync_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 IOS_CHROME_BROWSER_SIGNIN_DESKTOP_PROMOTION_SYNC_SERVICE_FACTORY_H_
+#define IOS_CHROME_BROWSER_SIGNIN_DESKTOP_PROMOTION_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 ios {
+class ChromeBrowserState;
+}
+
+class DesktopPromotionSyncService;
+
+// Singleton that owns all DesktopPromotionSyncService and associates them with
+// ios::ChromeBrowserState.
+class DesktopPromotionSyncServiceFactory
+    : public BrowserStateKeyedServiceFactory {
+ public:
+  static DesktopPromotionSyncService* GetForBrowserState(
+      ios::ChromeBrowserState* browser_state);
+  static DesktopPromotionSyncServiceFactory* GetInstance();
+
+ private:
+  friend struct base::DefaultSingletonTraits<
+      DesktopPromotionSyncServiceFactory>;
+
+  DesktopPromotionSyncServiceFactory();
+  ~DesktopPromotionSyncServiceFactory() override;
+
+  // BrowserStateKeyedServiceFactory implementation.
+  std::unique_ptr<KeyedService> BuildServiceInstanceFor(
+      web::BrowserState* context) const override;
+  bool ServiceIsNULLWhileTesting() const override;
+
+  DISALLOW_COPY_AND_ASSIGN(DesktopPromotionSyncServiceFactory);
+};
+
+#endif  // IOS_CHROME_BROWSER_SIGNIN_DESKTOP_PROMOTION_SYNC_SERVICE_FACTORY_H_