[Sync] USS: Implement SimpleMetadataChangeList.

sync/internal_api/public/simple_metadata_change_list.cc

Index: sync/internal_api/public/simple_metadata_change_list.cc
diff --git a/sync/internal_api/public/simple_metadata_change_list.cc b/sync/internal_api/public/simple_metadata_change_list.cc
index 999eda69b578b04b29fab330af0d735b683bc66b..e358dda3a115ab5be569fcd989eb7b2f376f65ad 100644
--- a/sync/internal_api/public/simple_metadata_change_list.cc
+++ b/sync/internal_api/public/simple_metadata_change_list.cc
@@ -12,24 +12,38 @@ SimpleMetadataChangeList::~SimpleMetadataChangeList() {}
 
 void SimpleMetadataChangeList::UpdateDataTypeState(
     const sync_pb::DataTypeState& data_type_state) {
-  // TODO(skym): Implementation.
+  state_change_.reset(new DataTypeStateChange{UPDATE, data_type_state});
+}
+
+void SimpleMetadataChangeList::ClearDataTypeState() {
+  state_change_.reset(new DataTypeStateChange{CLEAR});
 }
 
 void SimpleMetadataChangeList::UpdateMetadata(
     const std::string& client_tag,
     const sync_pb::EntityMetadata& metadata) {
-  // TODO(skym): Implementation.
+  metadata_changes_[client_tag] = {UPDATE, metadata};
 }
 
-void SimpleMetadataChangeList::ClearDataTypeState() {
-  // TODO(skym): Implementation.
+void SimpleMetadataChangeList::ClearMetadata(const std::string& client_tag) {
+  metadata_changes_[client_tag] = {CLEAR, sync_pb::EntityMetadata()};
 }
 
-void SimpleMetadataChangeList::ClearMetadata(const std::string& client_tag) {
-  // TODO(skym): Implementation.
+const SimpleMetadataChangeList::MetadataChanges&
+SimpleMetadataChangeList::GetMetadataChanges() const {
+  return metadata_changes_;
+}
+
+bool SimpleMetadataChangeList::HasDataTypeStateChange() const {
+  return state_change_.get() != nullptr;
+}
+
+const SimpleMetadataChangeList::DataTypeStateChange&
+SimpleMetadataChangeList::GetDataTypeStateChange() const {
+  return *state_change_.get();
 }
 
-void SimpleMetadataChangeList::TranfserChanges(
+void SimpleMetadataChangeList::TransferChanges(
     ModelTypeStore* store,
     ModelTypeStore::WriteBatch* write_batch) {
   // TODO(skym): Implementation.