Enable ARC for //ios/web_view/internal/translate/*.m.

ios/web_view/internal/translate/cwv_translate_manager_impl.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/web_view/internal/translate/cwv_translate_manager_impl.h"
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "components/translate/core/browser/translate_manager.h"
 #include "components/translate/core/browser/translate_ui_delegate.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation CWVTranslateManagerImpl {
   std::unique_ptr<translate::TranslateUIDelegate> _translateUIDelegate;
 }
 
 - (instancetype)initWithTranslateManager:(translate::TranslateManager*)manager
                           sourceLanguage:(const std::string&)source
                           targetLanguage:(const std::string&)target {
   if ((self = [super init])) {
     DCHECK(manager);
     _translateUIDelegate = base::MakeUnique<translate::TranslateUIDelegate>(
         manager->GetWeakPtr(), source, target);
   }
   return self;
 }
 
 #pragma mark CRIWVTranslateManager methods
 
 - (void)translate {
   _translateUIDelegate->Translate();
 }
 
 - (void)revertTranslation {
   _translateUIDelegate->RevertTranslation();
 }
 
 @end