Mojo C++ bindings: Remove more use_new_wrapper_types=false.

components/safe_json/utility/safe_json_parser_mojo_impl.cc

 // 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.
 
 #include "components/safe_json/utility/safe_json_parser_mojo_impl.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/json/json_reader.h"
 #include "base/values.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 
 namespace safe_json {
 
 SafeJsonParserMojoImpl::SafeJsonParserMojoImpl() = default;
 
 SafeJsonParserMojoImpl::~SafeJsonParserMojoImpl() = default;
 
 // static
 void SafeJsonParserMojoImpl::Create(
     mojo::InterfaceRequest<mojom::SafeJsonParser> request) {
   mojo::MakeStrongBinding(base::MakeUnique<SafeJsonParserMojoImpl>(),
                           std::move(request));
 }
 
-void SafeJsonParserMojoImpl::Parse(const mojo::String& json,
+void SafeJsonParserMojoImpl::Parse(const std::string& json,
                                    const ParseCallback& callback) {
   int error_code;
   std::string error;
   std::unique_ptr<base::Value> value = base::JSONReader::ReadAndReturnError(
-      json.get(), base::JSON_PARSE_RFC, &error_code, &error);
+      json, base::JSON_PARSE_RFC, &error_code, &error);
   base::ListValue wrapper;
   if (value) {
     wrapper.Append(std::move(value));
-    callback.Run(wrapper, nullptr);
+    callback.Run(wrapper, base::nullopt);
   } else {
-    callback.Run(wrapper, error);
+    callback.Run(wrapper, base::make_optional(std::move(error)));
   }
 }
 
 }  // namespace safe_json