Fix tabs duplication when restoring last closed window.

components/sessions/core/persistent_tab_restore_service.cc

Index: components/sessions/core/persistent_tab_restore_service.cc
diff --git a/components/sessions/core/persistent_tab_restore_service.cc b/components/sessions/core/persistent_tab_restore_service.cc
index 7548edb925a5b5861663a74d2fd5cd46ddf7eb36..f0689a431b811a8ed277078a71a358d23f8ee448 100644
--- a/components/sessions/core/persistent_tab_restore_service.cc
+++ b/components/sessions/core/persistent_tab_restore_service.cc
@@ -950,6 +950,10 @@ void PersistentTabRestoreService::DeleteLastSession() {
   return delegate_->DeleteLastSession();
 }
 
+bool PersistentTabRestoreService::IsRestoring() const {
+  return helper_.IsRestoring();
+}
+
 void PersistentTabRestoreService::Shutdown() {
   return delegate_->Shutdown();
 }