HTML5/JavaScript File with Canvas doesn't work with Chrome&Firefox on windows 8 but works with all browsers on windows 7. why?
Fabric.js thinks that your Chrome/Firefox have touch enabled so it attaches itself to touch events instead of mouse events.
It is not too clear to me whether this is a bug in Chrome/Firefox or in fabric or both.
See this https://github.com/kangax/fabric.js/issues/670 and also this https://github.com/kangax/fabric.js/issues/450
I am assuming your Windows 7 laptop did not have touch. This meant that all browsers had to capture mouse/touchpad events. However, if you had a Windows 8 touch laptop, the browsers can have different input sources (e.g. touchpad or touchscreen). Different browsers may use different implementations of handling each input causing this discrepancy which you are seeing.