You can find some helpful resources here (not all are HTML5). Also I found the Phaser framework to be very helpful when building HTML5 games. It's made by the same guys that made Flixel for Flash. It has been released recently so the documentation is a bit scarce but they are working on it. You can also find a lot of helpful resources in the forum and get a pretty fast response when opening a thread.
Unfortunately I don't have experience with Chrome extensions so I can't give you advice on that part. But as far as I see there are some games in the store that are Canvas based. Maybe you're running into some security restrictions.
Thanks, I will check all these out more thoroughly when I have more time later. I am still just learning about chrome extensions so I will continue to read about them and see if I can fix the problem when I have more knowledge about them. Thanks for these resources they look very helpful and what i had in mind!