[Sync] Remove ModelError::IsSet() in favor of base::Optional.

components/sync/device_info/device_info_sync_bridge.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 "components/sync/device_info/device_info_sync_bridge.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 95 matching lines @@
       base::Bind(&DeviceInfoSyncBridge::OnStoreCreated, base::AsWeakPtr(this)));
 }
 
 DeviceInfoSyncBridge::~DeviceInfoSyncBridge() {}
 
 std::unique_ptr<MetadataChangeList>
 DeviceInfoSyncBridge::CreateMetadataChangeList() {
   return WriteBatch::CreateMetadataChangeList();
 }
 
-ModelError DeviceInfoSyncBridge::MergeSyncData(
+base::Optional<ModelError> DeviceInfoSyncBridge::MergeSyncData(
     std::unique_ptr<MetadataChangeList> metadata_change_list,
     EntityDataMap entity_data_map) {
   DCHECK(has_provider_initialized_);
   DCHECK(change_processor()->IsTrackingMetadata());
   const DeviceInfo* local_info =
       local_device_info_provider_->GetLocalDeviceInfo();
   // If our dependency was yanked out from beneath us, we cannot correctly
   // handle this request, and all our data will be deleted soon.
   if (local_info == nullptr) {
-    return ModelError();
+    return {};
   }
 
   // Local data should typically be near empty, with the only possible value
   // corresponding to this device. This is because on signout all device info
   // data is blown away. However, this simplification is being ignored here and
   // a full difference is going to be calculated to explore what other bridge
   // implementations may look like.
   std::set<std::string> local_guids_to_put;
   for (const auto& kv : all_data_) {
     local_guids_to_put.insert(kv.first);
@@ skipping 20 matching lines @@
     }
   }
 
   for (const std::string& guid : local_guids_to_put) {
     change_processor()->Put(guid, CopyToEntityData(*all_data_[guid]),
                             metadata_change_list.get());
   }
 
   batch->TransferMetadataChanges(std::move(metadata_change_list));
   CommitAndNotify(std::move(batch), has_changes);
-  return ModelError();
+  return {};
 }
 
-ModelError DeviceInfoSyncBridge::ApplySyncChanges(
+base::Optional<ModelError> DeviceInfoSyncBridge::ApplySyncChanges(
     std::unique_ptr<MetadataChangeList> metadata_change_list,
     EntityChangeList entity_changes) {
   DCHECK(has_provider_initialized_);
   const DeviceInfo* local_info =
       local_device_info_provider_->GetLocalDeviceInfo();
   // If our dependency was yanked out from beneath us, we cannot correctly
   // handle this request, and all our data will be deleted soon.
   if (local_info == nullptr) {
-    return ModelError();
+    return {};
   }
 
   std::unique_ptr<WriteBatch> batch = store_->CreateWriteBatch();
   bool has_changes = false;
   for (EntityChange& change : entity_changes) {
     const std::string guid = change.storage_key();
     // Each device is the authoritative source for itself, ignore any remote
     // changes that have our local cache guid.
     if (guid == local_info->guid()) {
       continue;
     }
 
     if (change.type() == EntityChange::ACTION_DELETE) {
       has_changes |= DeleteSpecifics(guid, batch.get());
     } else {
       const DeviceInfoSpecifics& specifics =
           change.data().specifics.device_info();
       DCHECK(guid == specifics.cache_guid());
       StoreSpecifics(base::MakeUnique<DeviceInfoSpecifics>(specifics),
                      batch.get());
       has_changes = true;
     }
   }
 
   batch->TransferMetadataChanges(std::move(metadata_change_list));
   CommitAndNotify(std::move(batch), has_changes);
-  return ModelError();
+  return {};
 }
 
 void DeviceInfoSyncBridge::GetData(StorageKeyList storage_keys,
                                    DataCallback callback) {
   auto batch = base::MakeUnique<MutableDataBatch>();
   for (const auto& key : storage_keys) {
     const auto& iter = all_data_.find(key);
     if (iter != all_data_.end()) {
       DCHECK_EQ(key, iter->second->cache_guid());
       batch->Put(key, CopyToEntityData(*iter->second));
@@ skipping 156 matching lines @@
 }
 
 void DeviceInfoSyncBridge::LoadMetadataIfReady() {
   if (has_data_loaded_ && has_provider_initialized_) {
     store_->ReadAllMetadata(base::Bind(&DeviceInfoSyncBridge::OnReadAllMetadata,
                                        base::AsWeakPtr(this)));
   }
 }
 
 void DeviceInfoSyncBridge::OnReadAllMetadata(
-    ModelError error,
+    base::Optional<ModelError> error,
     std::unique_ptr<MetadataBatch> metadata_batch) {
-  if (error.IsSet()) {
-    change_processor()->ReportError(error);
+  if (error) {
+    change_processor()->ReportError(error.value());
     return;
   }
 
   change_processor()->OnMetadataLoaded(std::move(metadata_batch));
   ReconcileLocalAndStored();
 }
 
 void DeviceInfoSyncBridge::OnCommit(Result result) {
   if (result != Result::SUCCESS) {
     change_processor()->ReportError(FROM_HERE, "Failed a write to store.");
@@ skipping 76 matching lines @@
 
 int DeviceInfoSyncBridge::CountActiveDevices(const Time now) const {
   return std::count_if(all_data_.begin(), all_data_.end(),
                        [now](ClientIdToSpecifics::const_reference pair) {
                          return DeviceInfoUtil::IsActive(
                              GetLastUpdateTime(*pair.second), now);
                        });
 }
 
 }  // namespace syncer