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

ios/chrome/test/earl_grey/smoke_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 <UIKit/UIKit.h>
 #import <XCTest/XCTest.h>
 
 #import "ios/chrome/test/app/tab_test_util.h"
 #import "ios/chrome/test/earl_grey/chrome_earl_grey_ui.h"
 #import "ios/chrome/test/earl_grey/chrome_matchers.h"
 #import "ios/chrome/test/earl_grey/chrome_test_case.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 // Test case to verify that EarlGrey tests can be launched and perform basic UI
 // interactions.
 @interface SmokeTestCase : ChromeTestCase
 @end
 
 @implementation SmokeTestCase
 
 // Tests that the tools menu is tappable.
 - (void)testTapToolsMenu {
   [[EarlGrey selectElementWithMatcher:chrome_test_util::ToolsMenuButton()]
       performAction:grey_tap()];
 }
 
 // Tests that a tab can be opened.
 - (void)testOpenTab {
   [ChromeEarlGreyUI openNewTab];
   GREYAssertEqual(2, chrome_test_util::GetMainTabCount(), @"Expected 2 tabs.");
 }
 @end