Hi Cheng,
We have an almost finished Web API that keeps getting pushed down in priority on the backlog. So, at the moment, I’m afraid I can’t offer you a straightforward solution, and I don’t know when the Web API could get high enough priority.
In the meantime, you might be able to use or take inspiration from Overwolf and the Tobii EyeX for Overwolf API in some way. It’s a long shot, I know. The Overwolf Browsers are based on Chromium, and the Tobii EyeX for Overwolf API is accessible from javascript using the Overwolf Development Kit (ODK). You can find more info here:
http://developers.overwolf.com/eye-tracker-getting-started/
http://developers.overwolf.com/tobii-api-references/