Open tab in Firefox with scroll and zoom (but zoom works strange with browser.zoom.siteSpecific = true)

openTabWithScrollAndZoom.js

var textZoom = 1.5;
var fullZoom = 1;
var scrollX = 0;
var scrollY = 200;

var tab = gBrowser.addTab("https://addons.mozilla.org/");
var browser = tab.linkedBrowser;

if(scrollX || scrollY) {
	var scrollTimer = setInterval(function() {
		var win = browser.contentWindow;
		win.scrollTo(scrollX, scrollY);
		if(win.scrollX == scrollX && win.scrollY == scrollY) {
			clearInterval(scrollTimer);
			scrollTimer = 0;
			browser.removeEventListener("load", onLoad, true);
		}
	}, 50);
	var onLoad = function(e) {
		browser.removeEventListener("load", onLoad, true);
		if(scrollTimer) {
			clearInterval(scrollTimer);
			scrollTimer = 0;
		}
		browser.contentWindow.scrollTo(scrollX, scrollY);
	};
	browser.addEventListener("load", onLoad, true);
}
if(textZoom != 1 || fullZoom != 1) {
	// Note: correctly works only with browser.zoom.siteSpecific = false
	var viewer = browser.markupDocumentViewer;
	viewer.textZoom = textZoom;
	viewer.fullZoom = fullZoom;
}