[USS] implement CreateMetadataChangeList and GetClientTag

components/history/core/browser/history_backend.cc

Index: components/history/core/browser/history_backend.cc
diff --git a/components/history/core/browser/history_backend.cc b/components/history/core/browser/history_backend.cc
index 2ab8db29706c31618fd98fa350acc6caad45a35c..5c4b7bdb817335310d4161183f81a576ccafa9e9 100644
--- a/components/history/core/browser/history_backend.cc
+++ b/components/history/core/browser/history_backend.cc
@@ -889,6 +889,40 @@ bool HistoryBackend::IsExpiredVisitTime(const base::Time& time) {
   return time < expirer_.GetCurrentExpirationTime();
 }
 
+bool HistoryBackend::UpdateSyncMetadata(
+    syncer::ModelType model_type,
+    const std::string& storage_key,
+    const sync_pb::EntityMetadata& metadata) {
+  DCHECK_EQ(model_type, syncer::TYPED_URLS)
+      << "Only the TYPED_URLS model type is supported";
+
+  return db_->UpdateSyncMetadata(storage_key, metadata);
+}
+
+bool HistoryBackend::ClearSyncMetadata(syncer::ModelType model_type,
+                                       const std::string& storage_key) {
+  DCHECK_EQ(model_type, syncer::TYPED_URLS)
+      << "Only the TYPED_URLS model type is supported";
+
+  return db_->ClearSyncMetadata(storage_key);
+}
+
+bool HistoryBackend::UpdateModelTypeState(
+    syncer::ModelType model_type,
+    const sync_pb::ModelTypeState& model_type_state) {
+  DCHECK_EQ(model_type, syncer::TYPED_URLS)
+      << "Only the TYPED_URLS model type is supported";
+
+  return db_->UpdateModelTypeState(model_type_state);
+}
+
+bool HistoryBackend::ClearModelTypeState(syncer::ModelType model_type) {
+  DCHECK_EQ(model_type, syncer::TYPED_URLS)
+      << "Only the TYPED_URLS model type is supported";
+
+  return db_->ClearModelTypeState();
+}
+
 void HistoryBackend::SetPageTitle(const GURL& url,
                                   const base::string16& title) {
   if (!db_)