こんな感じ？
gBrowser.mPanelContainer.addEventListener("dblclick", function(aEvent) {
if (aEvent.button == 2) {
var target = aEvent.target;
while (target) {
if ((target instanceof HTMLAnchorElement || target instanceof HTMLAreaElement)
&& target.hasAttribute("href")) {
aEvent.preventDefault();
aEvent.stopPropagation();
document.getElementById("contentAreaContextMenu").hidePopup();
var docURL = target.ownerDocument.location.href;
urlSecurityCheck(target.href, docURL, Ci.nsIScriptSecurityManager.DISALLOW_SCRIPT);
gBrowser.loadOneTab(target.href, docURL ? makeURI(docURL) : null, null, null, false, false);
return;
}
target = target.parentNode;
}
}
}, true);