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

ios/public/provider/chrome/browser/signin/chrome_identity_service.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/public/provider/chrome/browser/signin/chrome_identity_service.h"
 
 #include "ios/public/provider/chrome/browser/signin/chrome_identity_interaction_manager.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace ios {
 
 ChromeIdentityService::ChromeIdentityService() {}
 
 ChromeIdentityService::~ChromeIdentityService() {
   for (auto& observer : observer_list_)
     observer.OnChromeIdentityServiceWillBeDestroyed();
 }
 
 void ChromeIdentityService::DismissDialogs() {}
@@ skipping 121 matching lines @@
   for (auto& observer : observer_list_)
     observer.OnAccessTokenRefreshFailed(identity, user_info);
 }
 
 void ChromeIdentityService::FireProfileDidUpdate(ChromeIdentity* identity) {
   for (auto& observer : observer_list_)
     observer.OnProfileUpdate(identity);
 }
 
 }  // namespace ios