This is a 15" 2010 model that came with OS X 10.6 and now has 10.10 installed. After turning the computer on I can hear the startup chime and the power adapter indicator light lights up. The Apple logo and a progress bar appear, but after that there's only a blank white screen.
There are some pixel anomalies, what appears to be scanlines and slightly distorted colors that look like it's running in 16-bit color depth.
I have tried following the official instructions, i.e. reset the PRAM/NVRAM and SMC, tried booting in safe mode (same symptoms, but after that it seems to boot automatically in safe mode since the loading takes a lot longer).
Also I recently installed Homebrew if it might have to do with this.