Why does "waiting" or "waitFor" dissapear in my code? - google-chrome-extension

Question

OK Ive updated the code to be as small as possible and still get the error...although now the question isnt quite right...it should now be "Why does waitFor jump out of the sandbox?" (but Ive been told not to change questions for a post, sorry if this is bad form). If you install this extension and follow the below instructions youll see waitFor get transferred to out side the content scripts sandbox.
To see this error.....
Go to....
https://www.facebook.com/groups/382415791793391/
..wait for the page to fully load.
Then click on the tab "Testy Testy" to cause the page to refresh.
Have a look in the console and youll see "You shouldnt be able to see this".
The console output for me looks like this....
chekcpage
waitFor
(19)waitFor
pop
attach contentNodeRemoved
chekcpage
waitFor
removing
added
attach contentNodeRemoved
chekcpage
waitFor
(156+)You shouldnt be able to see this
myscript.js
script = function(old) {
window.variableInUnsafeWindow = "You shouldnt be able to see this";
}
function exec(fn) {
var script = document.createElement('script');
script.setAttribute("type", "application/javascript");
script.textContent = '(' + fn + ')();';
document.documentElement.appendChild(script); // run the script
document.documentElement.removeChild(script); // clean up
}
exec(script);
window.onpopstate = function(event) {
console.debug('pop');
checkPage();
};
function waitFor(query, delay) {
if (typeof(variableInUnsafeWindow) == "undefined") {
console.debug('waitFor');
found = document.documentElement.querySelector(query);
if (!found) {
window.setTimeout("(" + waitFor + ")('" + query + "'," + delay + ");", delay);
}
} else {
console.debug(variableInUnsafeWindow);
window.setTimeout("(" + waitFor + ")('" + query + "'," + delay + ");", delay);
}
}
function contentNodeRemoved() {
console.debug('removing');
document.querySelector('div#contentCol').removeEventListener('DOMNodeRemoved', contentNodeRemoved, false);
document.querySelector('div#contentCol').addEventListener('DOMNodeInserted', contentNodeAdded, false);
}
function contentNodeAdded() {
console.debug('added');
document.querySelector('div#contentCol').removeEventListener('DOMNodeInserted', contentNodeAdded, false);
checkPage();
}
function checkPage() {
if (document.querySelector('div#contentCol')) {
console.debug('attach contentNodeRemoved');
var node = document.querySelector('div#contentCol');
node.addEventListener('DOMNodeRemoved', contentNodeRemoved, false);
}
console.debug('chekcpage');
waitFor('ul#group_mall_382415791793391', 300);
}
checkPage();
manifest.json
{
"name": "Facebook - Group member ban icon",
"description": "Puts an X after a users name on the groups page for banning. Unfortunately the X show on groups your not an Admin of still.",
"content_scripts": [{
"matches": ["*://*.facebook.com/*"],
"js": ["myscript.js"],
"run_at": "document_start"
}],
"permissions": ["tabs"],
"icons": {
"16": "icon.png",
"48": "icon48.png",
"128": "icon128.png"
},
"version": "1.0"
}