This is gomeboycolor, a Gameboy Color emulator, written in Go, ported to WebAssembly.
The performance is not great, and it's not a perfect emulator, but most games should work. I coded this a few years ago and decided to try and port it to WebAssembly.
Performance, at least for this application, is very sketchy in Chrome in comparison to Firefox and Safari.
This is a known issue and is being tracked by chromium/v8/8227
You might find keyboard controls and the 'Stop' button become unresponsive in Chrome, try adjusting the frame rate lock
Read this blog post for more information