EDIT: appears a user was able to recover from bootlooping, so not hard bricking.
Quote from https://old.reddit.com/r/GooglePixel/comments/178jj3i/need_h... below:
They escalated me to someone on the hardware team that sounded like they have been around for a while XD. But here's what I was able to do: From the fastboot menu (using the power + vol down button to boot the phone) select "Recovery mode" then when the phone goes to the No Command screen, hold the power button for 1 second then press the vol up button and release both at the same time. This will give you a command prompt of sorts. Go to factory wipe/reset and vioala. You can reload your phone. Sure it sucks but if you were stuck like I was this is good enough.
EDIT2: