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

ios/chrome/test/earl_grey/chrome_util.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.
 
 #include "ios/chrome/test/earl_grey/chrome_util.h"
 
 #import <EarlGrey/EarlGrey.h>
 
 #import "ios/chrome/browser/ui/toolbar/toolbar_controller.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
 #import "ios/testing/wait_util.h"
 #import "ios/web/public/test/earl_grey/web_view_matchers.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 const NSTimeInterval kWaitForToolbarAnimationTimeout = 1.0;
 }  // namespace
 
 namespace chrome_test_util {
 
 void AssertToolbarNotVisible() {
   ConditionBlock condition = ^{
     id<GREYMatcher> toolsMenuButton =
         grey_allOf(grey_accessibilityID(kToolbarToolsMenuButtonIdentifier),
@@ skipping 19 matching lines @@
         assertWithMatcher:grey_notNil()
                     error:&error];
     return error == nil;
   };
   GREYAssert(testing::WaitUntilConditionOrTimeout(
                  kWaitForToolbarAnimationTimeout, condition),
              @"The toolbar is not visible.");
 }
 
 }  // namespace chrome_test_util