Fix tabs duplication when restoring last closed window.

components/sessions/core/tab_restore_service_helper.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/tab_restore_service_helper.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <iterator>
@@ skipping 242 matching lines @@
 
   if (!restoring_tab_in_window) {
     entries_.erase(entry_iterator);
   }
 
   restoring_ = false;
   NotifyTabsChanged();
   return live_tabs;
 }
 
+bool TabRestoreServiceHelper::IsRestoring() const {
+  return restoring_;
+}
+
 void TabRestoreServiceHelper::NotifyTabsChanged() {
   FOR_EACH_OBSERVER(TabRestoreServiceObserver, observer_list_,
                     TabRestoreServiceChanged(tab_restore_service_));
 }
 
 void TabRestoreServiceHelper::NotifyLoaded() {
   FOR_EACH_OBSERVER(TabRestoreServiceObserver, observer_list_,
                     TabRestoreServiceLoaded(tab_restore_service_));
 }
 
@@ skipping 211 matching lines @@
         tab.browser_id = new_id;
     }
   }
 }
 
 base::Time TabRestoreServiceHelper::TimeNow() const {
   return time_factory_ ? time_factory_->TimeNow() : base::Time::Now();
 }
 
 }  // namespace sessions