device/bluetooth: Add I/O watcher for audio data retrieval triggered by state change.

chromeos/dbus/bluetooth_media_transport_client.cc

 // Copyright 2014 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 "chromeos/dbus/bluetooth_media_transport_client.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
@@ skipping 223 matching lines @@
 
     dbus::FileDescriptor fd;
     uint16_t read_mtu;
     uint16_t write_mtu;
 
     // Parse the response.
     dbus::MessageReader reader(response);
     if (reader.PopFileDescriptor(&fd) &&
         reader.PopUint16(&read_mtu) &&
         reader.PopUint16(&write_mtu)) {
-      callback.Run(fd, read_mtu, write_mtu);
+      fd.CheckValidity();
+      DCHECK(fd.is_valid());
+
+      VLOG(1) << "OnAcquireSuccess - fd: "<<  fd.value()
+              <<", read MTU: " << read_mtu
+              <<", write MTU: " << write_mtu;
+
+      // The ownership of the file descriptor is transferred to the user
+      // application.
+      callback.Run(&fd, read_mtu, write_mtu);
       return;
     }
 
     error_callback.Run(
         kUnexpectedResponse,
         "Failed to retrieve file descriptor, read MTU and write MTU.");
   }
 
   // Called when a response for a failed method call is received.
   void OnError(const ErrorCallback& error_callback,
@@ skipping 27 matching lines @@
 }
 
 BluetoothMediaTransportClient::~BluetoothMediaTransportClient() {
 }
 
 BluetoothMediaTransportClient* BluetoothMediaTransportClient::Create() {
   return new BluetoothMediaTransportClientImpl();
 }
 
 }  // namespace chromeos