Use OnceCallback on Mojo interfaces in //chrome/common/media_router

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 "base/bind.h"
+#include "base/callback_helpers.h"
 #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) {
+    DeviceDescriptionCallback callback) {

[mark a. foltz, 2017/05/09 22:28:44]

Can this just be a base::RepeatingCallback instead of copying?

[tzik, 2017/05/11 09:00:30]

So, the callback is not from Mojo-generated code? OK, reverted the code and
updated the callback type to RepeatingCallback.

[zhaobin, 2017/05/11 17:38:57]

The callback is from mojo-generated code. 

using DeviceDescriptionCallback =
chrome::mojom::DialDeviceDescriptionParser::ParseDialDeviceDescriptionCallback;

[tzik, 2017/05/15 06:28:15]

Right, the callback type was from Mojo. But, as the callback object itself is
not created by Mojo-generated code, it seems able to have separate typedef, and
leave it legacy callback now, as this CL do now.

   DVLOG(2) << "Start parsing device description...";
   DCHECK(thread_checker_.CalledOnValidThread());
 
   DCHECK(callback);
+  auto copyable_callback = base::AdaptCallbackForRepeating(std::move(callback));
 
   if (!utility_process_mojo_client_) {
     DVLOG(2) << "Start utility process in background...";
     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(callback, nullptr));
+        base::Bind(copyable_callback, nullptr));
 
     // 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,
-                                                                      callback);
+  utility_process_mojo_client_->service()->ParseDialDeviceDescription(
+      xml_text, copyable_callback);
 }
 
 }  // namespace media_router