[ObjC ARC] Converts ios/web:ios_web_net_unittests to ARC.

ios/web/net/request_group_util_unittest.mm

 // Copyright 2014 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/net/request_group_util.h"
 
 #import <Foundation/Foundation.h>
 #include <stddef.h>
 
-#import "base/mac/scoped_nsobject.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 // Checks that all newly generated groupID are unique and that there are no
 // duplicates.
 TEST(RequestGroupUtilTest, RequestGroupID) {
-  base::scoped_nsobject<NSMutableSet> set([[NSMutableSet alloc] init]);
+  NSMutableSet* set = [[NSMutableSet alloc] init];
   const size_t kGenerated = 2000;
   for (size_t i = 0; i < kGenerated; ++i)
     [set addObject:web::GenerateNewRequestGroupID()];
   EXPECT_EQ(kGenerated, [set count]);
 }
 
 // Tests that the ExtractRequestGroupIDFromUserAgent function behaves as
 // intended.
 TEST(RequestGroupUtilTest, ExtractRequestGroupIDFromUserAgent) {
   EXPECT_FALSE(web::ExtractRequestGroupIDFromUserAgent(nil));
   EXPECT_FALSE(web::ExtractRequestGroupIDFromUserAgent(
       @"Lynx/2.8.1pre.9 libwww-FM/2.14"));
   EXPECT_FALSE(web::ExtractRequestGroupIDFromUserAgent(@"    "));
   EXPECT_TRUE([web::ExtractRequestGroupIDFromUserAgent(@"Mozilla/3.04 (WinNT)")
       isEqualToString:@"WinNT"]);
 }