[Sync] Split UserEventService into interface and impl, add fake impl, add unit tests.

components/sync/user_events/user_event_service_impl.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 "components/sync/user_events/user_event_service.h"
+#include "components/sync/user_events/user_event_service_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/feature_list.h"
 #include "base/memory/ptr_util.h"
 #include "base/rand_util.h"
 #include "components/sync/driver/sync_driver_switches.h"
 #include "components/sync/driver/sync_service.h"
 #include "components/sync/model/model_type_sync_bridge.h"
 #include "components/sync/user_events/user_event_sync_bridge.h"
 
 using sync_pb::UserEventSpecifics;
 
 namespace syncer {
 
-UserEventService::UserEventService(SyncService* sync_service,
-                                   std::unique_ptr<UserEventSyncBridge> bridge)
+UserEventServiceImpl::UserEventServiceImpl(
+    SyncService* sync_service,
+    std::unique_ptr<UserEventSyncBridge> bridge)
     : sync_service_(sync_service),
       bridge_(std::move(bridge)),
       session_id_(base::RandUint64()) {
   // TODO(skym): Subscribe to events about field trial membership changing.
 }
 
-UserEventService::~UserEventService() {}
+UserEventServiceImpl::~UserEventServiceImpl() {}
 
-void UserEventService::Shutdown() {}
+void UserEventServiceImpl::Shutdown() {}
 
-void UserEventService::RecordUserEvent(
+void UserEventServiceImpl::RecordUserEvent(
     std::unique_ptr<UserEventSpecifics> specifics) {
-  if (CanRecordEvent(*specifics)) {
+  if (ShouldRecordEvent(*specifics)) {
     DCHECK(!specifics->has_session_id());
     specifics->set_session_id(session_id_);
     bridge_->RecordUserEvent(std::move(specifics));
   }
 }
 
-void UserEventService::RecordUserEvent(const UserEventSpecifics& specifics) {
+void UserEventServiceImpl::RecordUserEvent(
+    const UserEventSpecifics& specifics) {
   RecordUserEvent(base::MakeUnique<UserEventSpecifics>(specifics));
 }
 
-base::WeakPtr<ModelTypeSyncBridge> UserEventService::GetSyncBridge() {
+base::WeakPtr<ModelTypeSyncBridge> UserEventServiceImpl::GetSyncBridge() {
   return bridge_->AsWeakPtr();
 }
 
-bool UserEventService::CanRecordEvent(const UserEventSpecifics& specifics) {
+bool UserEventServiceImpl::ShouldRecordEvent(
+    const UserEventSpecifics& specifics) {
   // We only record events if the user is syncing history and has not enabled
   // a custom passphrase. The type HISTORY_DELETE_DIRECTIVES is enabled in and
   // only in this exact scenario.
   return base::FeatureList::IsEnabled(switches::kSyncUserEvents) &&
          sync_service_ != nullptr && sync_service_->IsEngineInitialized() &&
          sync_service_->GetPreferredDataTypes().Has(HISTORY_DELETE_DIRECTIVES);
 }
 
-void RegisterDependentFieldTrial(const std::string& trial_name,
-                                 UserEventSpecifics::EventCase event_case) {
+void UserEventServiceImpl::RegisterDependentFieldTrial(
+    const std::string& trial_name,
+    UserEventSpecifics::EventCase event_case) {
   // TODO(skym): Implementation.
 }
 
 }  // namespace syncer