[ObjC ARC] Converts ios/web:earl_grey_test_support to ARC.

ios/web/public/test/earl_grey/js_test_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.
 
 #import "ios/web/public/test/earl_grey/js_test_util.h"
 
 #import <EarlGrey/EarlGrey.h>
 #import <WebKit/WebKit.h>
 
 #include "base/timer/elapsed_timer.h"
 #import "ios/testing/wait_util.h"
 #import "ios/web/interstitials/web_interstitial_impl.h"
 #import "ios/web/public/web_state/js/crw_js_injection_receiver.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using testing::kWaitForJSCompletionTimeout;
 using testing::WaitUntilConditionOrTimeout;
 
 namespace web {
 
 // Evaluates the given |script| on |interstitial|.
 void ExecuteScriptForTesting(web::WebInterstitialImpl* interstitial,
                              NSString* script,
                              web::JavaScriptResultBlock handler) {
   DCHECK(interstitial);
@@ skipping 22 matching lines @@
       is_window_id_injected = [result isEqual:@0];
     }
     is_timeout = timeout < timer.Elapsed();
   }
   GREYAssertFalse(is_timeout, @"windowID injection timed out");
   GREYAssertFalse(is_unrecoverable_error, @"script execution error");
 }
 
 id ExecuteJavaScript(WebState* web_state,
                      NSString* javascript,
-                     NSError** out_error) {
+                     NSError* __autoreleasing* out_error) {
   __block bool did_complete = false;
   __block id result = nil;
   CRWJSInjectionReceiver* receiver = web_state->GetJSInjectionReceiver();
   [receiver executeJavaScript:javascript
             completionHandler:^(id value, NSError* error) {
               did_complete = true;
               result = [value copy];
               if (out_error)
                 *out_error = [error copy];
             }];
 
   // Wait for completion.
   BOOL suceeded = WaitUntilConditionOrTimeout(kWaitForJSCompletionTimeout, ^{
     return did_complete;
   });
   GREYAssert(suceeded, @"Script execution timed out");
 
-  if (out_error)
-    [*out_error autorelease];
-  return [result autorelease];
+  return result;
 }
 
 id ExecuteScriptOnInterstitial(WebState* web_state, NSString* script) {
   web::WebInterstitialImpl* interstitial =
       static_cast<web::WebInterstitialImpl*>(web_state->GetWebInterstitial());
 
   __block id script_result = nil;
   __block bool did_finish = false;
   web::ExecuteScriptForTesting(interstitial, script, ^(id result, NSError*) {
     script_result = [result copy];
     did_finish = true;
   });
   BOOL suceeded = WaitUntilConditionOrTimeout(kWaitForJSCompletionTimeout, ^{
     return did_finish;
   });
   GREYAssert(suceeded, @"Script execution timed out");
-  return [script_result autorelease];
+  return script_result;
 }
 
 }  // namespace web