Revert of Deletes mojo::Callback

device/serial/serial_service_impl.cc

Index: device/serial/serial_service_impl.cc
diff --git a/device/serial/serial_service_impl.cc b/device/serial/serial_service_impl.cc
index 97ad57f86cc24084a6f94d100da6b2142aa65824..a66abea8d0a2f723607f1cc1d4a14c5ec3395d2d 100644
--- a/device/serial/serial_service_impl.cc
+++ b/device/serial/serial_service_impl.cc
@@ -56,7 +56,8 @@
                                    ui_task_runner, base::Passed(&request)));
 }
 
-void SerialServiceImpl::GetDevices(const GetDevicesCallback& callback) {
+void SerialServiceImpl::GetDevices(
+    const mojo::Callback<void(mojo::Array<serial::DeviceInfoPtr>)>& callback) {
   callback.Run(GetDeviceEnumerator()->GetDevices());
 }