i have the exact same problem!
i use windows 8.1 with a amd 7870 gpu and my game is 60fps constantly in chrome.
for the first time ever i used node webkit to see how it works and i have 8!!! fps.
i just read that when exporting it has even better performance.
i downloaded the OP demo capx and from 60fps in chrome i see 24 fps in node webkit.
any idea what is happening?