Bug 831781 - Add support for ouya gamepad joystick-based scrolling. r=Cwiiis
Bug 831781 - Extract a getAdjustedZoomFactor method to encapsulate the zoom edge resistance. No functional change. r=
Bug 831781 - Add support for zooming in/out with gamepad zoom buttons. r=
Bug 831781 - Some touchups to the code to make it more consistent and robust. r=