[ObjC ARC] Converts ios/chrome/browser/web:eg_tests to ARC.

ios/chrome/browser/web/js_print_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 <EarlGrey/EarlGrey.h>
 #import <XCTest/XCTest.h>
 #include <map>
 
 #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"
 #import "ios/web/public/test/http_server.h"
 #import "ios/web/public/test/http_server_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 // Test case for bringing up the print dialog when a web site's JavaScript runs
 // "window.print".
 @interface JSPrintTestCase : ChromeTestCase
 @end
 
 @implementation JSPrintTestCase
 
 // Tests that tapping a button with onclick='window.print' brings up the
 // print dialog.
 - (void)testWebPrintButton {
@@ skipping 20 matching lines @@
       assertWithMatcher:grey_sufficientlyVisible()];
 
   // Clean up and close print dialog.
   id<GREYMatcher> cancelButton =
       grey_allOf(grey_accessibilityLabel(@"Cancel"),
                  grey_accessibilityTrait(UIAccessibilityTraitButton), nil);
   [[EarlGrey selectElementWithMatcher:cancelButton] performAction:grey_tap()];
 }
 
 @end