Chrome瀏覽器mousemove event 的 bug

I found a strange issue that ...

[Chrome browser trigger "mousemove" event when mouse do not move!!]

Date： 2012.08.28 pm 03:33
Version: Chrome 21.0.1180.83 m

as below:

html tag:

<div id="zone" style="height: 100px; width: 100px;">

javascript code:

var Z=document.getElementById("zone");
Z.addEventListener("mousemove",function(){console.log("Hello");},false);

Then put the mouse onto "zone" , "Hello" words present in console per second.

What a XXX Chrome now is.