var evt = document.createEvent("KeyEvents");
evt.initKeyEvent(
"keydown",
true,
true,
null,
false, // holds Ctrl key
true, // holds Alt key
true, // holds Shift key
false, // holds Meta key
evt.DOM_VK_R, // presses a special key,
0 // presses a normal key, e.g. "A".charCodeAt(0),
);
gBrowser.contentDocument.documentElement.dispatchEvent(evt);;