[ObjC ARC] Converts ios/web/shell/test to ARC.

ios/web/shell/test/earl_grey/shell_matchers.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/shell/test/earl_grey/shell_matchers.h"
 
 #import "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/testing/earl_grey/matchers.h"
 #include "ios/testing/earl_grey/wait_util.h"
 #import "ios/web/public/web_state/web_state.h"
 #import "ios/web/public/test/earl_grey/web_view_matchers.h"
 #import "ios/web/shell/test/app/web_shell_test_util.h"
 #import "ios/web/shell/view_controller.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 id<GREYMatcher> webViewContainingText(const std::string& text) {
   WebState* web_state = shell_test_util::GetCurrentWebState();
   return webViewContainingText(std::move(text), web_state);
 }
 
 id<GREYMatcher> webViewCssSelector(const std::string& selector) {
   WebState* web_state = shell_test_util::GetCurrentWebState();
   return webViewCssSelector(std::move(selector), web_state);
@@ skipping 21 matching lines @@
       return [text_field.text isEqualToString:base::SysUTF8ToNSString(text)];
     });
     return YES;
   };
 
   DescribeToBlock describe = ^(id<GREYDescription> description) {
     [description appendText:@"address field containing "];
     [description appendText:base::SysUTF8ToNSString(text)];
   };
 
-  return [[[GREYElementMatcherBlock alloc] initWithMatchesBlock:matches
-                                               descriptionBlock:describe]
-      autorelease];
+  return [[GREYElementMatcherBlock alloc] initWithMatchesBlock:matches
+                                              descriptionBlock:describe];
 }
 
 id<GREYMatcher> backButton() {
   return grey_accessibilityLabel(kWebShellBackButtonAccessibilityLabel);
 }
 
 id<GREYMatcher> forwardButton() {
   return grey_accessibilityLabel(kWebShellForwardButtonAccessibilityLabel);
 }
 
 id<GREYMatcher> addressField() {
   return grey_accessibilityLabel(kWebShellAddressFieldAccessibilityLabel);
 }
 
 }  // namespace web