[Media Router] Parse device description xml in utility process

chrome/browser/media/router/discovery/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/safe_dial_device_description_parser.h"
+
+#include <utility>
+
+#include "chrome/common/extensions/chrome_utility_extensions_messages.h"
+#include "chrome/grit/generated_resources.h"
+#include "content/public/browser/browser_thread.h"
+#include "ui/base/l10n/l10n_util.h"
+
+using content::BrowserThread;
+using content::UtilityProcessHost;
+
+namespace media_router {
+
+SafeDialDeviceDescriptionParser::SafeDialDeviceDescriptionParser() {}
+
+SafeDialDeviceDescriptionParser::~SafeDialDeviceDescriptionParser() {}
+
+void SafeDialDeviceDescriptionParser::Start(
+    const std::string& xml_text,
+    const DeviceDescriptionCallback& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(!utility_process_mojo_client_);
+  DCHECK(callback);
+
+  device_description_callback_ = callback;
+
+  utility_process_mojo_client_ =
+      base::MakeUnique<content::UtilityProcessMojoClient<
+          extensions::mojom::DialDeviceDescriptionParser>>(
+          l10n_util::GetStringUTF16(
+              IDS_UTILITY_PROCESS_DIAL_DEVICE_DESCRIPTION_PARSER_NAME));
+
+  utility_process_mojo_client_->set_error_callback(base::Bind(
+      &SafeDialDeviceDescriptionParser::ParseDialDeviceDescriptionFailed,

[mark a. foltz, 2017/03/17 19:05:46]

Conventionally, methods used only as callbacks start with "On", so suggest
OnParseDeviceDescriptionFailed

[zhaobin, 2017/03/18 00:17:38]

Done.

+      this));
+  utility_process_mojo_client_->Start();  // Start the utility process

[mark a. foltz, 2017/03/17 19:05:46]

I assume this starts the process in the background, and the call below is queued
up until the Mojo message pipe has been established to the service running in
the utility process.

[zhaobin, 2017/03/18 00:17:38]

Done.

+  utility_process_mojo_client_->service()->ParseDialDeviceDescription(
+      xml_text,
+      base::Bind(
+          &SafeDialDeviceDescriptionParser::ParseDialDeviceDescriptionDone,

[mark a. foltz, 2017/03/17 19:05:46]

OnParseDeviceDescriptionComplete

[zhaobin, 2017/03/18 00:17:38]

Done.

+          this));
+}
+
+void SafeDialDeviceDescriptionParser::ParseDialDeviceDescriptionDone(
+    bool result,
+    const media_router::DialDeviceDescription& device_description,
+    const std::string& logging_xml) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);

[mark a. foltz, 2017/03/17 19:05:46]

Slightly prefer base::ThreadChecker.  I suppose that DCHECK_CURRENTLY_ON saves
allocating a class member, but makes the class slightly harder to test.  Not
sure why we have both ways of checking thread safety.

[zhaobin, 2017/03/18 00:17:38]

Done.

+
+  utility_process_mojo_client_.reset();  // Terminate the utility process.
+
+  DCHECK(!device_description_callback_.is_null());
+  device_description_callback_.Run(result, device_description, logging_xml);
+}
+
+void SafeDialDeviceDescriptionParser::ParseDialDeviceDescriptionFailed() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  utility_process_mojo_client_.reset();  // Terminate the utility process.
+
+  DCHECK(!device_description_callback_.is_null());
+  device_description_callback_.Run(false, media_router::DialDeviceDescription(),
+                                   "");
+}
+
+}  // namespace media_router