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

ios/chrome/browser/context_menu/context_menu_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>
 
 #include "base/strings/sys_string_conversions.h"
 #include "ios/chrome/browser/ui/ui_util.h"
 #include "ios/chrome/grit/ios_strings.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
 #import "ios/chrome/test/app/settings_test_util.h"
 #import "ios/chrome/test/app/tab_test_util.h"
 #include "ios/chrome/test/app/web_view_interaction_test_util.h"
 #import "ios/chrome/test/earl_grey/chrome_actions.h"
 #import "ios/chrome/test/earl_grey/chrome_assertions.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 "ios/chrome/test/earl_grey/chrome_util.h"
 #import "ios/testing/wait_util.h"
 #import "ios/web/public/test/earl_grey/web_view_matchers.h"
 #import "ios/web/public/test/http_server.h"
 #import "ios/web/public/test/http_server_util.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using chrome_test_util::ButtonWithAccessibilityLabelId;
 
 namespace {
 const char kUrlChromiumLogoPage[] =
     "http://ios/testing/data/http_server_files/chromium_logo_page.html";
 const char kUrlChromiumLogoImg[] =
     "http://ios/testing/data/http_server_files/chromium_logo.png";
 const char kUrlInitialPage[] = "http://scenarioContextMenuOpenInNewTab";
 const char kUrlDestinationPage[] = "http://destination";
 const char kChromiumImageID[] = "chromium_image";
@@ skipping 209 matching lines @@
   SelectTabAtIndexInCurrentMode(1U);
 
   // Verify url and tab count.
   [[EarlGrey selectElementWithMatcher:chrome_test_util::OmniboxText(
                                           destinationURL.GetContent())]
       assertWithMatcher:grey_notNil()];
   chrome_test_util::AssertMainTabCount(2U);
 }
 
 @end