[Media Router] Parse device description xml in utility process

chrome/browser/media/router/discovery/dial/safe_dial_device_description_parser.cc

+// Copyright 2017 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 "chrome/browser/media/router/discovery/dial/safe_dial_device_description_parser.h"
+
+#include <utility>
+
+#include "chrome/grit/generated_resources.h"
+#include "content/public/browser/browser_thread.h"
+#include "ui/base/l10n/l10n_util.h"
+
+namespace media_router {
+
+SafeDialDeviceDescriptionParser::SafeDialDeviceDescriptionParser() {}
+
+SafeDialDeviceDescriptionParser::~SafeDialDeviceDescriptionParser() {}
+
+void SafeDialDeviceDescriptionParser::Start(
+    const std::string& xml_text,
+    const DeviceDescriptionCallback& callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!utility_process_mojo_client_);
+  DCHECK(callback);
+
+  device_description_callback_ = callback;
+
+  utility_process_mojo_client_ =
+      base::MakeUnique<content::UtilityProcessMojoClient<
+          chrome::mojom::DialDeviceDescriptionParser>>(
+          l10n_util::GetStringUTF16(
+              IDS_UTILITY_PROCESS_DIAL_DEVICE_DESCRIPTION_PARSER_NAME));
+
+  utility_process_mojo_client_->set_error_callback(base::Bind(
+      &SafeDialDeviceDescriptionParser::OnParseDeviceDescriptionFailed,
+      base::Unretained(this)));
+
+  // This starts utility process in the background.
+  utility_process_mojo_client_->Start();
+
+  // This call is queued up until the Mojo message pipe has been established to
+  // the service running in the utility process.
+  utility_process_mojo_client_->service()->ParseDialDeviceDescription(
+      xml_text,
+      base::Bind(
+          &SafeDialDeviceDescriptionParser::OnParseDeviceDescriptionComplete,
+          base::Unretained(this)));
+}
+
+void SafeDialDeviceDescriptionParser::OnParseDeviceDescriptionComplete(
+    bool result,
+    const base::Optional<media_router::DialDeviceDescription>&
+        device_description) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  utility_process_mojo_client_.reset();  // Terminate the utility process.
+
+  DCHECK(!device_description_callback_.is_null());

[dcheng, 2017/03/22 09:53:02]

Nit: be consistent about using is_null() or omitting it in DCHECKs (line 24
omits, while line 58 and 67 both use is_null)

[zhaobin, 2017/03/22 19:18:52]

Done.

+  device_description_callback_.Run(result, device_description);
+}
+
+void SafeDialDeviceDescriptionParser::OnParseDeviceDescriptionFailed() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  utility_process_mojo_client_.reset();  // Terminate the utility process.
+
+  DCHECK(!device_description_callback_.is_null());
+  device_description_callback_.Run(false, base::nullopt);
+}
+
+}  // namespace media_router