If you have access to the Google Universal Type-C Charger 60W that is shipped with the Google Chromebook Pixel (2015) and are curious if the Google charger can work with your Samsung Galaxy S8, you should have no problems using the Google charger to provide USB Power Delivery charging to the Samsung Galaxy S8.
We start charging the Samsung Galaxy S8 with the Google Universal Type-C Charger 60W with the phone's battery being 23% charged. The Google charger can be seen to offer 15 watts (5 volts @ 3 amps), 36 watts (12 volts @ 3 amps), and 60 watts (20 volts @ 3 amps) over USB Power Delivery to the Samsung Galaxy S8.
The Samsung Galaxy S8 then requests to pull 15 watts (5 volts @ 3 amps) which the Google charger accepts.
The Samsung Galaxy S8 later also shows off its power sinking capabilities of 2.5 watts (5 volts @ 0.5 amps) and a variable of 2.5 to 6 watts (5 to 12 volts @ 0.5 amps).
We can confirm from the power graph that USB Power Delivery is working fine with the Google Universal Type-C Charger 60W providing around 10 watts (5 volts @ 2 amps) to the Samsung Galaxy S8 from a 23% charged battery.