The Huawei Google Nexus 6P is shipped with a 15 watts based Huawei power adapter but the phone doesn't support the USB Power Delivery fast charging protocol over USB Type-C. Fortunately you can still keep the phone charged by plugging in to certain Window PC's like the Dell XPS 15 9550 Laptop when on the road. Unless the Dell laptop is connected to AC power, the Huawei Google Nexus 6P may very well drains the Dell's battery charge.
Here we see how well the Huawei Google Nexus 6P gets powered when attached to the Thunderbolt 3 based USB Type-C port on the Dell XPS 15 9550 Laptop. After selecting the option to charge the phone under the phone's USB charging settings, we use the Granite River Labs GRL-USB-PD-A1 test app to see how the phone communicates with the PC. As expected there's no response from the Nexus phone when being repeatedly offered 15 watts (5 volts @ 3 amps) by the Dell laptop since the phone can't use USB Power Delivery.
From the power graph we can see unstable charging in the first 6 minutes before the Huawei Google Nexus 6P eventually pulls around 1.5 to 2 amps @ 4.6 volts while the phone is being used. While the Nexus phone only gets max 9.2 watts power from the Dell XPS 15 9550 Laptop as observed, you can still charge the phone with the PC but not as quickly as with the phone's own Huawei charger.