You can use the Plugable USB-C Docking Station with Power Delivery / Charging (Model UD-CA1) to add more interface ports to your Chromebook Pixel (2015).
Here we can see that Plugable USB-C Docking Station adds an Ethernet port which shows up in the Chromebook Pixel (2015)'s Settings scren.
After connecting a LG 4K Ultra HD Smart TV with webOS 2.0 (2015) to the HDMI port of the Plugable USB-C Docking Station, I could extend the Chromebook Pixel (2015)'s screen to the LG TV.
Using USB Power Delivery analysis software from Granite River Labs, we can see the Plugable USB-C Docking Station offerings three power profiles 15 watts (5 volts @ 3 amps), 36 watts (12 volts @ 3 amps), and 100 watts (20 volts @ 5 amps).
The Chromebook Pixel (2015) then requests 20 volts @ 3 amps to get charged from the Plugable USB-C Docking Station.
You can use the Plugable USB-C Docking Station to easily add Ethernet, USB, HDMI, and audio ports while charging the Chromebook Pixel (2015).