[ObjC ARC] Converts components/dom_distiller/ios:ios to ARC.

components/dom_distiller/ios/distiller_page_factory_ios.mm

 // Copyright 2015 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/dom_distiller/ios/distiller_page_factory_ios.h"
 
 #include "base/memory/ptr_util.h"
 #include "components/dom_distiller/ios/distiller_page_ios.h"
 #include "ios/web/public/browser_state.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace dom_distiller {
 
 DistillerPageFactoryIOS::DistillerPageFactoryIOS(
     web::BrowserState* browser_state)
     : browser_state_(browser_state) {}
 
 DistillerPageFactoryIOS::~DistillerPageFactoryIOS() {}
 
 std::unique_ptr<DistillerPage> DistillerPageFactoryIOS::CreateDistillerPage(
     const gfx::Size& view_size) const {
   return base::MakeUnique<DistillerPageIOS>(browser_state_);
 }
 
 std::unique_ptr<DistillerPage>
 DistillerPageFactoryIOS::CreateDistillerPageWithHandle(
     std::unique_ptr<SourcePageHandle> handle) const {
   return base::MakeUnique<DistillerPageIOS>(browser_state_);
 }
 
 }  // namespace dom_distiller