[ObjC ARC] Converts ios/chrome/browser/autocomplete to ARC.

ios/chrome/browser/autocomplete/autocomplete_scheme_classifier_impl.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 "ios/chrome/browser/autocomplete/autocomplete_scheme_classifier_impl.h"
 
 #include "base/logging.h"
 #include "base/strings/string_util.h"
 #include "ios/chrome/browser/chrome_url_util.h"
 #include "url/url_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 AutocompleteSchemeClassifierImpl::AutocompleteSchemeClassifierImpl() {}
 
 AutocompleteSchemeClassifierImpl::~AutocompleteSchemeClassifierImpl() {}
 
 metrics::OmniboxInputType::Type
 AutocompleteSchemeClassifierImpl::GetInputTypeForScheme(
     const std::string& scheme) const {
   DCHECK_EQ(scheme, base::ToLowerASCII(scheme));
   if (base::IsStringASCII(scheme) &&
       (IsHandledProtocol(scheme) || (scheme == url::kJavaScriptScheme))) {
     return metrics::OmniboxInputType::URL;
   }
 
   // iOS does not support registration of external schemes.
   return metrics::OmniboxInputType::INVALID;
 }