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

ios/web/web_state/js/context_menu_js_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.
 
 #include <vector>
 
 #import <CoreGraphics/CoreGraphics.h>
 #import <Foundation/Foundation.h>
 
 #include "base/macros.h"
 #include "base/strings/stringprintf.h"
 #import "ios/web/public/test/web_test_with_web_state.h"
 #import "ios/web/public/web_state/ui/crw_web_view_proxy.h"
 #import "ios/web/public/web_state/ui/crw_web_view_scroll_view_proxy.h"
 #import "ios/web/public/web_state/web_state.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 // Unit tests for ios/web/web_state/js/resources/context_menu.js.
 
 namespace {
 
 // Test coordinates and expected result for __gCrWeb.getElementFromPoint call.
 struct TestCoordinatesAndExpectedValue {
   TestCoordinatesAndExpectedValue(CGFloat x, CGFloat y, id expected_value)
       : x(x), y(y), expected_value(expected_value) {}
   CGFloat x = 0;
   CGFloat y = 0;
@@ skipping 161 matching lines @@
     expected_result = @{
       @"src" : [NSString stringWithFormat:@"%sfoo", BaseUrl().c_str()],
       @"referrerPolicy" : @"default",
     };
     // Make sure the returned JSON does not have an 'href' key.
     EXPECT_NSEQ(expected_result, result);
   }
 }
 
 }  // namespace web