How to Pinch Zoom on device with no touchscreen, like an Android Stick?

I have some Android TV "sticks", such as the RK3188, which is basically a tablet minus the screen. You control them using keyboard and a mouse. The problem is, I have no way to zoom in or out in the browser. There's no way for me to do a "pinch" gesture, and Ctrl +/- etc. don't seem to work in any browser, like Chrome, FireFox, and Dolphin. I'm using the box as a display screen in a public area and not being able to scale the content to fit the whole TV is a serious limitation. EDIT: Double tap only offers 2 zoom levels "close" and "far".