If you are on the road, the Belkin USB-C Car Charger + Cable can charge many of your USB Type-C devices that support USB Power Delivery like the Google Chromebook Pixel (2015).
Using software from Granite River Labs to capture the USB Power Delivery Protocol transaction, we can see that the Belkin USB-C Car Charger + Cable is able to supply 15 watts (5 volts @ 3 amps) and 27 watts (9 volts @ 3 amps) over the USB Type-C connector.
The Chromebook Pixel (2015) requests 27 watts (9 volts @ 3 amps) of charging from the Belkin USB-C Car Charger + Cable.
We can confirm from the oscilloscope screenshot below that the Chromebook Pixel (2015) is pulling around 3 amps at 9 volts from the Belkin USB-C Car Charger + Cable.