Factor out a BluetoothChannelMac base class and a BluetoothRfcommChannelMac subclass.

device/bluetooth/bluetooth_channel_mac.mm

+// 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 "device/bluetooth/bluetooth_channel_mac.h"
+
+#include "base/logging.h"
+
+namespace device {
+
+BluetoothChannelMac::BluetoothChannelMac() : socket_(NULL) {
+}
+
+BluetoothChannelMac::~BluetoothChannelMac() {
+}
+
+void BluetoothChannelMac::SetSocket(BluetoothSocketMac* socket) {
+  DCHECK(!socket_);
+  socket_ = socket;
+}
+
+}  // namespace device