[USS] implement CreateMetadataChangeList and GetClientTag

components/history/core/browser/history_backend.cc

 // Copyright (c) 2012 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/history/core/browser/history_backend.h"
 
 #include <algorithm>
 #include <functional>
 #include <list>
 #include <map>
@@ skipping 871 matching lines @@
   // TODO(brettw) bug 1140015: Add an "add page" notification so the history
   // views can keep in sync.
   NotifyURLsModified(changed_urls);
   ScheduleCommit();
 }
 
 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_)
     return;
 
   // Search for recent redirects which should get the same title. We make a
   // dummy list containing the exact URL visited if there are no redirects so
   // the processing below can be the same.
   RedirectList dummy_list;
   RedirectList* redirects;
@@ skipping 1759 matching lines @@
   // transaction is currently open.
   db_->CommitTransaction();
   db_->Vacuum();
   db_->BeginTransaction();
   db_->GetStartDate(&first_recorded_time_);
 
   return true;
 }
 
 }  // namespace history