[ObjC ARC] Converts ios/web/public/test/fakes:fakes to ARC.

ios/web/public/test/fakes/test_java_script_dialog_presenter.mm

Index: ios/web/public/test/fakes/test_java_script_dialog_presenter.mm
diff --git a/ios/web/public/test/fakes/test_java_script_dialog_presenter.mm b/ios/web/public/test/fakes/test_java_script_dialog_presenter.mm
index 2e44213214ba5c60c015893fa12fc6e03d199ed6..2403a03b0bdbfe8924eb1a66638f6f759d85ced3 100644
--- a/ios/web/public/test/fakes/test_java_script_dialog_presenter.mm
+++ b/ios/web/public/test/fakes/test_java_script_dialog_presenter.mm
@@ -4,6 +4,10 @@
 
 #import "ios/web/public/test/fakes/test_java_script_dialog_presenter.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 TestJavaScriptDialog::TestJavaScriptDialog() = default;
@@ -28,12 +32,12 @@ void TestJavaScriptDialogPresenter::RunJavaScriptDialog(
   dialog.web_state = web_state;
   dialog.origin_url = origin_url;
   dialog.java_script_dialog_type = java_script_dialog_type;
-  dialog.message_text.reset([message_text copy]);
-  dialog.default_prompt_text.reset([default_prompt_text copy]);
+  dialog.message_text = [message_text copy];
+  dialog.default_prompt_text = [default_prompt_text copy];
 
   requested_dialogs_.push_back(dialog);
 
-  callback.Run(callback_success_argument_, callback_user_input_argument_.get());
+  callback.Run(callback_success_argument_, callback_user_input_argument_);
 }
 
 void TestJavaScriptDialogPresenter::CancelDialogs(WebState* web_state) {