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

ios/web/url_scheme_util_unittest.mm

 // Copyright 2013 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/public/url_scheme_util.h"
 
 #import <Foundation/Foundation.h>
 
 #import "testing/gtest_mac.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 TEST(URLSchemeUtilTest, UrlHasWebScheme) {
   EXPECT_TRUE(UrlHasWebScheme(GURL("http://foo.com")));
   EXPECT_TRUE(UrlHasWebScheme(GURL("https://foo.com")));
   EXPECT_TRUE(UrlHasWebScheme(GURL("data:text/html;charset=utf-8,Hello")));
   EXPECT_FALSE(UrlHasWebScheme(GURL("about:blank")));
   EXPECT_FALSE(UrlHasWebScheme(GURL("chrome://settings")));
 }
 
 TEST(URLSchemeUtilTest, NSURLHasWebScheme) {
   EXPECT_TRUE(UrlHasWebScheme([NSURL URLWithString:@"http://foo.com"]));
   EXPECT_TRUE(UrlHasWebScheme([NSURL URLWithString:@"https://foo.com"]));
   EXPECT_TRUE(UrlHasWebScheme(
       [NSURL URLWithString:@"data:text/html;charset=utf-8,Hello"]));
   EXPECT_FALSE(UrlHasWebScheme([NSURL URLWithString:@"about:blank"]));
   EXPECT_FALSE(UrlHasWebScheme([NSURL URLWithString:@"chrome://settings"]));
 }
 
 }  // namespace web