Add Desktop iOS promotion logging to chrome ios app.

ios/chrome/browser/desktop_promotion/desktop_promotion_sync_service.cc

+// 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.
+
+#include "ios/chrome/browser/desktop_promotion/desktop_promotion_sync_service.h"
+
+#include "components/pref_registry/pref_registry_syncable.h"
+#include "components/prefs/pref_service.h"
+#include "ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.h"
+#include "ios/chrome/browser/pref_names.h"
+
+DesktopPromotionSyncService::DesktopPromotionSyncService(
+    PrefService* pref_service,
+    browser_sync::ProfileSyncService* sync_service)
+    : observer_(pref_service, sync_service) {}
+
+DesktopPromotionSyncService::~DesktopPromotionSyncService() = default;
+
+// static
+void DesktopPromotionSyncService::RegisterDesktopPromotionUserPrefs(
+    user_prefs::PrefRegistrySyncable* registry) {
+  registry->RegisterIntegerPref(
+      prefs::kDesktopIOSPromotionSMSEntryPoint, 0,
+      user_prefs::PrefRegistrySyncable::SYNCABLE_PRIORITY_PREF);
+  registry->RegisterIntegerPref(
+      prefs::kDesktopIOSPromotionShownEntryPoints, 0,
+      user_prefs::PrefRegistrySyncable::SYNCABLE_PRIORITY_PREF);
+  registry->RegisterDoublePref(
+      prefs::kDesktopIOSPromotionLastImpression, 0,
+      user_prefs::PrefRegistrySyncable::SYNCABLE_PRIORITY_PREF);
+  registry->RegisterBooleanPref(
+      prefs::kDesktopIOSPromotionDone, false,
+      user_prefs::PrefRegistrySyncable::SYNCABLE_PRIORITY_PREF);
+}