When you click the login button, the following function is called: launchPopup=function(){ window.open("/login/","AppLogin","resizable,scrollbars,status,width=600,height=400")}

Which opens https://foobar.withgoogle.com/login

There, an object a:

a = {

				message: '<span class="term-red">Error(6): Login unavailable. Try again later.</span>',
				logoutUrl: 'https://foobar.withgoogle.com/_ah/logout?continue=https://www.google.com/accounts/Logout%3Fcontinue%3Dhttps://appengine.google.com/_ah/logout%253Fcontinue%253Dhttps://foobar.withgoogle.com/denied/%26service%3Dah',
				redirectUrl: '/denied/',
				
				allow: false
			}

Is passed to the original window's handleAuth function:

window.handleAuth=function(a){ a.logoutUrl?window.location.href=a.redirectUrl:window.location.reload()}

It seems that the allow property of the object passed is never checked :(

Put more simply, you can redefine the handleAuth function to automatically set the allow property to true

window.handleAuth=function(a){ a.allow = true; a.logoutUrl?window.location.href=a.redirectUrl:window.location.reload()}

and then click the button.

But it won't help for the reasons explained above.

That was my thought too, although I'm not sure how it would be done.

I was thinking about a = document.getElementbyId("login"); a.addEvenListener("click",function(a){a.preventDefault()...}

Perhaps if one can avoid preventDefault the object login may has some href to the real login. Just guessing.