Implement a basic Site Engagement Score service.

chrome/browser/engagement/site_engagement_service_factory.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 "chrome/browser/engagement/site_engagement_service_factory.h"
+
+#include "chrome/browser/engagement/site_engagement_service.h"
+#include "chrome/browser/profiles/profile.h"
+#include "components/keyed_service/content/browser_context_dependency_manager.h"
+
+// static
+SiteEngagementService* SiteEngagementServiceFactory::GetForProfile(
+    Profile* profile) {
+  return static_cast<SiteEngagementService*>(
+      GetInstance()->GetServiceForBrowserContext(profile, true));
+}
+
+// static
+SiteEngagementServiceFactory* SiteEngagementServiceFactory::GetInstance() {
+  return Singleton<SiteEngagementServiceFactory>::get();
+}
+
+SiteEngagementServiceFactory::SiteEngagementServiceFactory()
+    : BrowserContextKeyedServiceFactory(
+          "SiteEngagementService",
+          BrowserContextDependencyManager::GetInstance()) {
+}
+
+SiteEngagementServiceFactory::~SiteEngagementServiceFactory() {
+}
+
+bool SiteEngagementServiceFactory::ServiceIsNULLWhileTesting() const {
+  return true;
+}
+
+KeyedService* SiteEngagementServiceFactory::BuildServiceInstanceFor(
+    content::BrowserContext* profile) const {
+  return new SiteEngagementService(static_cast<Profile*>(profile));
+}