Fix tabs duplication when restoring last closed window.

components/sessions/core/persistent_tab_restore_service.cc

 // Copyright 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/sessions/core/persistent_tab_restore_service.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
 #include <utility>
@@ skipping 932 matching lines @@
 }
 
 bool PersistentTabRestoreService::IsLoaded() const {
   return delegate_->IsLoaded();
 }
 
 void PersistentTabRestoreService::DeleteLastSession() {
   return delegate_->DeleteLastSession();
 }
 
+bool PersistentTabRestoreService::IsRestoring() const {
+  return helper_.IsRestoring();
+}
+
 void PersistentTabRestoreService::Shutdown() {
   return delegate_->Shutdown();
 }
 
 void PersistentTabRestoreService::LoadTabsFromLastSession() {
   delegate_->LoadTabsFromLastSession();
 }
 
 TabRestoreService::Entries* PersistentTabRestoreService::mutable_entries() {
   return &helper_.entries_;
 }
 
 void PersistentTabRestoreService::PruneEntries() {
   helper_.PruneEntries();
 }
 
 }  // namespace sessions