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

device/bluetooth/dbus/bluetooth_gatt_descriptor_service_provider_impl.cc

Index: device/bluetooth/dbus/bluetooth_gatt_descriptor_service_provider_impl.cc
diff --git a/device/bluetooth/dbus/bluetooth_gatt_descriptor_service_provider_impl.cc b/device/bluetooth/dbus/bluetooth_gatt_descriptor_service_provider_impl.cc
index f2b3de4b17778ff6ca811de33db303b272f6665c..a747797882bbd5b0a14d94549c69d7897a97399d 100644
--- a/device/bluetooth/dbus/bluetooth_gatt_descriptor_service_provider_impl.cc
+++ b/device/bluetooth/dbus/bluetooth_gatt_descriptor_service_provider_impl.cc
@@ -154,6 +154,7 @@ void BluetoothGattDescriptorServiceProviderImpl::Get(
   if (property_name == bluetooth_gatt_descriptor::kValueProperty) {
     DCHECK(delegate_);
     delegate_->GetValue(
+        dbus::ObjectPath(),
         base::Bind(&BluetoothGattDescriptorServiceProviderImpl::OnGet,
                    weak_ptr_factory_.GetWeakPtr(), method_call,
                    response_sender),
@@ -257,7 +258,7 @@ void BluetoothGattDescriptorServiceProviderImpl::Set(
   std::vector<uint8_t> value(bytes, bytes + length);
   DCHECK(delegate_);
   delegate_->SetValue(
-      value,
+      dbus::ObjectPath(), value,
       base::Bind(&BluetoothGattDescriptorServiceProviderImpl::OnSet,
                  weak_ptr_factory_.GetWeakPtr(), method_call, response_sender),
       base::Bind(&BluetoothGattDescriptorServiceProviderImpl::OnFailure,
@@ -297,6 +298,7 @@ void BluetoothGattDescriptorServiceProviderImpl::GetAll(
   // response in the success callback.
   DCHECK(delegate_);
   delegate_->GetValue(
+      dbus::ObjectPath(),
       base::Bind(&BluetoothGattDescriptorServiceProviderImpl::OnGetAll,
                  weak_ptr_factory_.GetWeakPtr(), method_call, response_sender),
       base::Bind(&BluetoothGattDescriptorServiceProviderImpl::OnFailure,