[ObjC ARC] Converts ios/web/public/test:test to ARC.

ios/web/public/test/test_redirect_observer.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/web/public/test/test_redirect_observer.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/supports_user_data.h"
 #import "ios/web/public/navigation_item.h"
 #import "ios/web/public/navigation_manager.h"
 #include "ios/web/public/web_state/navigation_context.h"
 #import "ios/web/public/web_state/web_state.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // The key under which TestRedirectObservers are stored in a WebState's user
 // data.
 const void* const kTestRedirectObserverKey = &kTestRedirectObserverKey;
 }  // namespace
 
 namespace web {
 
 #pragma mark - TestRedirectObserverUserDataWrapper
 
@@ skipping 66 matching lines @@
     // chain for that NavigationItem.
     expected_urls_.erase(url);
     RedirectChain redirect_chain;
     redirect_chain.original_url = url;
     redirect_chain.final_url = url;
     redirect_chains_[item] = redirect_chain;
   }
 }
 
 }  // namespace web