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

ios/web/web_state/context_menu_params_utils_unittest.mm

 // Copyright 2017 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/web_state/context_menu_params_utils.h"
 
 #include "base/strings/sys_string_conversions.h"
 #include "components/url_formatter/url_formatter.h"
 #include "ios/web/public/referrer_util.h"
 #import "ios/web/public/web_state/context_menu_params.h"
 #import "net/base/mac/url_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #import "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // Text values for the tapped element triggering the context menu.
 const char* kLinkUrl = "http://link.url/";
 const char* kSrcUrl = "http://src.url/";
 const char* kTitle = "title";
 const char* kReferrerPolicy = "always";
 const char* kLinkText = "link text";
 const char* kJavaScriptLinkUrl = "javascript://src.url/";
 const char* kDataUrl = "data://foo.bar/";
 }
@@ skipping 64 matching lines @@
 }
 
 // Tests title is set to nil if there is no title and src is a data URL.
 TEST_F(ContextMenuParamsUtilsTest, DictionaryConstructorTestDataTitle) {
   web::ContextMenuParams params = web::ContextMenuParamsFromElementDictionary(@{
     @"src" : @(kDataUrl),
   });
   EXPECT_EQ(params.src_url, GURL(kDataUrl));
   EXPECT_NSEQ(params.menu_title.get(), nil);
 }