[ARC] Converts parts of ios/web/web_state to ARC.

ios/web/web_state/error_translation_util.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.
 
 #import "ios/web/web_state/error_translation_util.h"
 
 #include <CFNetwork/CFNetwork.h>
 
 #import "base/ios/ns_error_util.h"
 #include "base/mac/scoped_nsobject.h"
 #include "net/base/net_errors.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 namespace {
 // Translates an iOS error to a net error using |net_error_code| as an
 // out-parameter.  Returns true if a valid translation was found.
 bool GetNetErrorFromIOSErrorCode(NSInteger ios_error_code,
                                  NSInteger* net_error_code) {
   DCHECK(net_error_code);
   bool translation_success = true;
   switch (ios_error_code) {
@@ skipping 141 matching lines @@
   DCHECK(error);
   NSString* net_error_domain =
       [NSString stringWithUTF8String:net::kErrorDomain];
   NSError* net_error = [NSError errorWithDomain:net_error_domain
                                            code:net_error_code
                                        userInfo:nil];
   return base::ios::ErrorWithAppendedUnderlyingError(error, net_error);
 }
 
 }  // namespace web