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

ios/chrome/test/app/static_html_view_test_util.mm

 // Copyright 2017 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 "ios/chrome/test/app/static_html_view_test_util.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/chrome/browser/ui/static_content/static_html_view_controller.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
 #import "ios/testing/wait_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace chrome_test_util {
 
 // Synchronously returns the result of executed JavaScript.
 id ExecuteScriptInStaticController(
     StaticHtmlViewController* html_view_controller,
     NSString* script) {
   __block id result = nil;
   __block bool did_finish = false;
   [html_view_controller executeJavaScript:script
                         completionHandler:^(id script_result, NSError* error) {
                           result = [script_result copy];
                           did_finish = true;
                         }];
 
   // If a timeout is reached, then return |result|, which should be nil;
   testing::WaitUntilConditionOrTimeout(testing::kWaitForJSCompletionTimeout, ^{
     return did_finish;
   });
 
-  return [result autorelease];
+  return result;
 }
 
 // Returns the StaticHtmlViewController for the given |web_state|. If none is
 // found, it returns nil.
 StaticHtmlViewController* GetStaticHtmlView(web::WebState* web_state) {
   // The WKWebView in a static HTML view isn't part of a
   // webState, but it does have the StaticHtmlViewController
   // as its navigation delegate. The WKWebView is the only child subview
   // of the web state's view.
   UIView* web_state_view = chrome_test_util::GetCurrentWebState()->GetView();
   WKWebView* web_view =
       base::mac::ObjCCast<WKWebView>(web_state_view.subviews.firstObject);
   return base::mac::ObjCCast<StaticHtmlViewController>(
       web_view.navigationDelegate);
 }
 
 bool StaticHtmlViewContainingText(web::WebState* web_state, std::string text) {
   StaticHtmlViewController* html_view_controller = GetStaticHtmlView(web_state);
   if (!html_view_controller) {
     return false;
   }
 
   id body = ExecuteScriptInStaticController(
       html_view_controller, @"document.body ? document.body.textContent : ''");
   return [body containsString:base::SysUTF8ToNSString(text)];
   return false;
 }
 }  // namespace chrome_test_util