How to prevent the browser from seeing my keystrokes?

My browser (chrome but I think it doesn't matter) receives events for keystrokes which are not intended for it. For example, I'm doing alt+tab in Mate and then I press escape (while still holding the alt). This has the intended effect of the alt+tab dialog disappearing without switching the window but also the unintended effect of the browser thinking I just pressed escape (which affects the web application I'm using). Looking for related questions I found this: https://unix.stackexchange.com/questions/36281/how-do-i-prevent-programs-from-sniffing-keystrokes-to-su-gksu but my case is a little different - I (kind of) trust the browser, I just don't want it to think that I've pressed a key. Is this something I can configure in xorg or in mate?