Google-chrome – How to change the length of time a tooltip stays open in Google Chrome

So as many of you know XKCD uses the tooltip to provide some extra funny information about the last comic. However sometimes the tooltips are long and while reading them it will go away. I then have to move my mouse back over the image to get the tooltip. When I'm using Ubuntu the tooltip stays open as long as I have my mouse over the image. How can I get this effect in Chrome?