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

chromeos/dbus/bluetooth_media_transport_client.h

 // 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.
 
 #ifndef CHROMEOS_DBUS_BLUETOOTH_MEDIA_TRANSPORT_CLIENT_H_
 #define CHROMEOS_DBUS_BLUETOOTH_MEDIA_TRANSPORT_CLIENT_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 80 matching lines @@
   ~BluetoothMediaTransportClient() override;
 
   // The ErrorCallback is used by media transport API methods to indicate
   // failure. It receives two arguments: the name of the error in |error_name|
   // and an optional message in |error_message|.
   typedef base::Callback<void(const std::string& error_name,
                               const std::string& error_message)> ErrorCallback;
 
   // The AcquireCallback is used by |Acquire| method of media tansport API tp
   // indicate the success of the method.
-  typedef base::Callback<void(const dbus::FileDescriptor& fd,

[armansito, 2015/03/12 03:42:54]

I would pass a "dbus::FileDescriptor*" here instead of const int fd. Please see
my comment in bluetooth_media_transport_client.cc.

[Miao, 2015/03/12 22:33:31]

Done.

+  typedef base::Callback<void(const int fd,
                               const uint16_t read_mtu,
                               const uint16_t write_mtu)> AcquireCallback;
 
   // Adds and removes observers for events on all remote Media Transports. Check
   // the |object_path| parameter of observer methods to determine which Media
   // Transport is issuing the event.
   virtual void AddObserver(Observer* observer) = 0;
   virtual void RemoveObserver(Observer* observer) = 0;
 
   virtual Properties* GetProperties(const dbus::ObjectPath& object_path) = 0;
@@ skipping 21 matching lines @@
  protected:
   BluetoothMediaTransportClient();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BluetoothMediaTransportClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_BLUETOOTH_MEDIA_TRANSPORT_CLIENT_H_