Waw, thank you, I wasn't aware of that :)
Yeh, you Only have to download and install Firefox first.
asm.js does not require Firefox and runs just fine in browsers like Chrome.
It just performs better in Firefox at the moment due to better support.
I did try the demos in the New Opera browser witch is as close as "browsers like Chrome" you can get. But it didn't work.
[0] http://blog.mozilla.org/press/2015/03/unity-5-ships-and-brin...
[1] https://blog.mozilla.org/blog/2015/02/24/unreal-engine-4-7-b...