[ObjC ARC] Converts ios/chrome/browser/ui/ntp/recent_tabs:recent_tabs to ARC.

ios/chrome/browser/ui/ntp/recent_tabs/recent_tabs_bridges.mm

 // Copyright 2014 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.
 
 #import "ios/chrome/browser/ui/ntp/recent_tabs/recent_tabs_bridges.h"
 
 #import "ios/chrome/browser/ui/ntp/recent_tabs/recent_tabs_table_view_controller.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace recent_tabs {
 
 #pragma mark - ClosedTabsObserverBridge
 
 ClosedTabsObserverBridge::ClosedTabsObserverBridge(
     RecentTabsPanelController* owner)
     : owner_(owner) {}
 
 ClosedTabsObserverBridge::~ClosedTabsObserverBridge() {}
 
 void ClosedTabsObserverBridge::TabRestoreServiceChanged(
     sessions::TabRestoreService* service) {
   [owner_ reloadClosedTabsList];
 }
 
 void ClosedTabsObserverBridge::TabRestoreServiceDestroyed(
     sessions::TabRestoreService* service) {
   [owner_ tabRestoreServiceDestroyed];
 }
 
 }  // namespace recent_tabs