[ObjC ARC] Converts ios/chrome/browser/signin:signin to ARC.

ios/chrome/browser/signin/profile_oauth2_token_service_ios_provider_impl.mm

 // Copyright 2016 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/signin/profile_oauth2_token_service_ios_provider_impl.h"
 
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
 #include "ios/chrome/browser/signin/constants.h"
 #include "ios/chrome/browser/signin/signin_util.h"
 #import "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #import "ios/public/provider/chrome/browser/signin/chrome_identity.h"
 #include "ios/public/provider/chrome/browser/signin/chrome_identity_service.h"
 #include "ios/public/provider/chrome/browser/signin/signin_error_provider.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // Returns the account info for |identity|.
 // Returns an empty account info if |identity| is nil.
 ProfileOAuth2TokenServiceIOSProvider::AccountInfo GetAccountInfo(
     ChromeIdentity* identity) {
   ProfileOAuth2TokenServiceIOSProvider::AccountInfo account_info;
   if (identity) {
     account_info.gaia = base::SysNSStringToUTF8([identity gaiaID]);
     account_info.email = GetCanonicalizedEmailForIdentity(identity);
   }
@@ skipping 73 matching lines @@
       if (provider->IsForbidden(error)) {
         return kAuthenticationErrorCategoryAuthorizationForbiddenErrors;
       }
       return kAuthenticationErrorCategoryAuthorizationErrors;
     case ios::SigninErrorCategory::NETWORK_ERROR:
       return kAuthenticationErrorCategoryNetworkServerErrors;
     case ios::SigninErrorCategory::USER_CANCELLATION_ERROR:
       return kAuthenticationErrorCategoryUserCancellationErrors;
   }
 }