[ObjC ARC] Converts ios/chrome/test/earl_grey:ios_chrome_device_check_egtests to ARC.

ios/chrome/test/earl_grey/device_check_egtest.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.
 
 #import <XCTest/XCTest.h>
 
 #import "ios/chrome/test/earl_grey/chrome_earl_grey.h"
 #import "ios/chrome/test/earl_grey/chrome_matchers.h"
 #import "ios/chrome/test/earl_grey/chrome_test_case.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using chrome_test_util::WebViewContainingText;
 
 // Test suite to verify Internet connectivity.
 @interface DeviceCheckTestCase : ChromeTestCase
 @end
 
 @implementation DeviceCheckTestCase
 
 // Verifies Internet connectivity by navigating to browsingtest.appspot.com.
 - (void)testNetworkConnection {
   [ChromeEarlGrey loadURL:GURL("http://browsingtest.appspot.com")];
   [[EarlGrey selectElementWithMatcher:WebViewContainingText("Window1")]
       assertWithMatcher:grey_notNil()];
 }
 
 @end