Add DBus plumbing and tests for sending devices with ATT read/writes.

device/bluetooth/dbus/bluetooth_gatt_descriptor_delegate_wrapper.cc

 // Copyright 2016 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/dbus/bluetooth_gatt_descriptor_delegate_wrapper.h"
 
 #include "device/bluetooth/bluez/bluetooth_local_gatt_descriptor_bluez.h"
 
 namespace bluez {
 
 BluetoothGattDescriptorDelegateWrapper::BluetoothGattDescriptorDelegateWrapper(
     BluetoothLocalGattServiceBlueZ* service,
     BluetoothLocalGattDescriptorBlueZ* descriptor)
-    : service_(service), descriptor_(descriptor) {}
+    : BluetoothGattAttributeValueDelegate(service), descriptor_(descriptor) {}
 
 void BluetoothGattDescriptorDelegateWrapper::GetValue(
+    const dbus::ObjectPath& device_path,
     const device::BluetoothLocalGattService::Delegate::ValueCallback& callback,
     const device::BluetoothLocalGattService::Delegate::ErrorCallback&
         error_callback) {
-  service_->GetDelegate()->OnDescriptorReadRequest(nullptr, descriptor_, 0,
-                                                   callback, error_callback);
+  service()->GetDelegate()->OnDescriptorReadRequest(
+      GetDeviceWithPath(device_path), descriptor_, 0, callback, error_callback);
 }
 
 void BluetoothGattDescriptorDelegateWrapper::SetValue(
+    const dbus::ObjectPath& device_path,
     const std::vector<uint8_t>& value,
     const base::Closure& callback,
     const device::BluetoothLocalGattService::Delegate::ErrorCallback&
         error_callback) {
-  service_->GetDelegate()->OnDescriptorWriteRequest(
-      nullptr, descriptor_, value, 0, callback, error_callback);
+  service()->GetDelegate()->OnDescriptorWriteRequest(
+      GetDeviceWithPath(device_path), descriptor_, value, 0, callback,
+      error_callback);
 }
 
 }  // namespace bluez