Safari 8.0 (Yosemite) returns nothing on mousemove

Question

I don't know if it has always been like that in Safari, but I'm having a problem with the mousemove event in Safari that works just well in Chrome (and FF).

With the following code :

document.addEventListener('mousemove', function(e) {
  console.log(e);
})

Chrome returns something like that:

But Safari only gives me that:

Do you have any idea why?

Thank you!