[USS] Add SyncMetadataStore interface

components/sync/model_impl/on_disk_metadata_change_list.cc

-// Copyright 2016 The Chromium Authors. All rights reserved.
+// 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/autofill/core/browser/webdata/autofill_metadata_change_list.h"
+#include "components/sync/model_impl/on_disk_metadata_change_list.h"
 
 #include "base/location.h"
 
 using base::Optional;
 using syncer::ModelError;
 
-namespace autofill {
+namespace syncer {
 
-AutofillMetadataChangeList::AutofillMetadataChangeList(AutofillTable* table,
-                                                       syncer::ModelType type)
+OnDiskMetadataChangeList::OnDiskMetadataChangeList(MetadataTable* table,
+                                                   syncer::ModelType type)
     : table_(table), type_(type) {
   DCHECK(table_);
-  // This should be changed as new autofill types are converted to USS.
-  DCHECK_EQ(syncer::AUTOFILL, type_);
 }
 
-AutofillMetadataChangeList::~AutofillMetadataChangeList() {
+OnDiskMetadataChangeList::~OnDiskMetadataChangeList() {
   DCHECK(!error_);
 }
 
-void AutofillMetadataChangeList::UpdateModelTypeState(
+void OnDiskMetadataChangeList::UpdateModelTypeState(
     const sync_pb::ModelTypeState& model_type_state) {
   if (error_) {
     return;
   }
 
   if (!table_->UpdateModelTypeState(type_, model_type_state)) {
     error_ = ModelError(FROM_HERE, "Failed to update ModelTypeState.");
   }
 }
 
-void AutofillMetadataChangeList::ClearModelTypeState() {
+void OnDiskMetadataChangeList::ClearModelTypeState() {
   if (error_) {
     return;
   }
 
   if (!table_->ClearModelTypeState(type_)) {
     error_ = ModelError(FROM_HERE, "Failed to clear ModelTypeState.");
   }
 }
 
-void AutofillMetadataChangeList::UpdateMetadata(
+void OnDiskMetadataChangeList::UpdateMetadata(
     const std::string& storage_key,
     const sync_pb::EntityMetadata& metadata) {
   if (error_) {
     return;
   }
 
   if (!table_->UpdateSyncMetadata(type_, storage_key, metadata)) {
     error_ = ModelError(FROM_HERE, "Failed to update entity metadata.");
   }
 }
 
-void AutofillMetadataChangeList::ClearMetadata(const std::string& storage_key) {
+void OnDiskMetadataChangeList::ClearMetadata(const std::string& storage_key) {
   if (error_) {
     return;
   }
 
   if (!table_->ClearSyncMetadata(type_, storage_key)) {
     error_ = ModelError(FROM_HERE, "Failed to clear entity metadata.");
   }
 }
 
-Optional<ModelError> AutofillMetadataChangeList::TakeError() {
+Optional<ModelError> OnDiskMetadataChangeList::TakeError() {
   Optional<ModelError> temp = error_;
   error_.reset();
   return temp;
 }
 
-}  // namespace autofill
+}  // namespace syncer