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

ios/chrome/test/earl_grey/chrome_earl_grey.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 "ios/chrome/test/earl_grey/chrome_earl_grey.h"
 
 #import <Foundation/Foundation.h>
 #import <WebKit/WebKit.h>
 
 #include "base/strings/sys_string_conversions.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
 #import "ios/chrome/test/app/history_test_util.h"
 #include "ios/chrome/test/app/navigation_test_util.h"
 #import "ios/testing/wait_util.h"
 #import "ios/web/public/test/earl_grey/js_test_util.h"
 #import "ios/web/public/test/web_view_interaction_test_util.h"
 #import "ios/web/public/web_state/js/crw_js_injection_receiver.h"
 #import "ios/web/public/web_state/web_state.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace chrome_test_util {
 
-id ExecuteJavaScript(NSString* javascript, NSError** out_error) {
+id ExecuteJavaScript(NSString* javascript,
+                     NSError* __unsafe_unretained* out_error) {
   __block bool did_complete = false;
   __block id result = nil;
   __block NSError* temp_error = nil;
   CRWJSInjectionReceiver* evaluator =
       chrome_test_util::GetCurrentWebState()->GetJSInjectionReceiver();
   [evaluator executeJavaScript:javascript
              completionHandler:^(id value, NSError* error) {
                did_complete = true;
                result = [value copy];
                temp_error = [error copy];
              }];
 
   // Wait for completion.
   GREYCondition* condition = [GREYCondition
       conditionWithName:@"Wait for JavaScript execution to complete."
                   block:^BOOL {
                     return did_complete;
                   }];
   [condition waitWithTimeout:testing::kWaitForJSCompletionTimeout];
   if (!did_complete)
     return nil;
-  [temp_error autorelease];
-  if (out_error)
-    *out_error = temp_error;
-  return [result autorelease];
+  if (out_error) {
+    NSError* __autoreleasing auto_released_error = temp_error;
+    *out_error = auto_released_error;
+  }
+  return result;
 }
 
 }  // namespace chrome_test_util
 
 @implementation ChromeEarlGrey
 
 #pragma mark - History Utilities
 
 + (void)clearBrowsingHistory {
   chrome_test_util::ClearBrowsingHistory();
@@ skipping 27 matching lines @@
 
 + (void)tapWebViewElementWithID:(NSString*)elementID {
   BOOL success =
       web::test::TapWebViewElementWithId(chrome_test_util::GetCurrentWebState(),
                                          base::SysNSStringToUTF8(elementID));
   GREYAssertTrue(success, @"Failed to tap web view element with ID: %@",
                  elementID);
 }
 
 @end