Javascript inexplicably disabled in appended xul:browser

I am having an extremely weird issue.

I append a xul:browser to the current window. Attributes are type=content and remote=true.

I load oauth pages in here. Javascript used to work absolutely fine in here. All of a sudden, the Allow/Deny buttons on Google OAuth page is not enabling. I tried simple alerts and javascript stuff from the contentWindow and it won’t work. I force removed the disabled attribute via privelaged javascript (from the framescript), and then the next page that loads from Google says “javascript is disabled, go back and try again”.

This was not happening just like 6 hours ago. I didn’t change anything.

I now even tested docShell.allowJavascript on the content and even each window that loads in the framescript with:

contentWindowArr[h].QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDocShell).allowJavascript

What can possibly be causing this?

allowJavascript is true everywhere I look.

Thanks

I checked the headers too, does any of these mean disable javascript?

https://accounts.google.com/AccountChooser

POST /AccountChooser HTTP/1.1
Host: accounts.google.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Firefox/45.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Referer: https://accounts.google.com/AccountChooser?.................
Cookie: ......................
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 447
.....................
HTTP/2.0 302 Found
X-Frame-Options: DENY
Cache-Control: no-cache, no-store, max-age=0, must-revalidate
Pragma: no-cache
Expires: Fri, 01 Jan 1990 00:00:00 GMT
Date: Mon, 07 Mar 2016 11:25:08 GMT
Location: https://accounts.google.com/o/oauth2/auth.............................
x-content-type-options: nosniff
X-XSS-Protection: 1; mode=block
Server: GSE
Content-Type: text/html; charset=UTF-8
Content-Encoding: gzip
Content-Length: 379
Set-Cookie: ..........
Alternate-Protocol: 443:quic,p=1
Alt-Svc: quic=":443"; ma=2592000; v="30,29,28,27,26,25"
X-Firefox-Spdy: h2