my.xfinity.com - site is not usable

[webcompat-bot]

URL: https://my.xfinity.com/?cid=cust

Browser / Version: Firefox 61.0
Operating System: Mac OS X 10.13
Tested Another Browser: Yes

Problem type: Site is not usable
Description: The top bar doesn't load
Steps to Reproduce:
None, just loading the url shows the issue

From webcompat.com with ❤️

[adamopenweb]

I can reproduce this in Firefox 61 for OSX but not in 59 or 60.

In the console we see:

TypeError: Constructor HTMLElement requires 'new'           polaris.js:1:96
Blocked loading mixed active content “http://ads.rubiconproject.com/ad/11648.js"

The mixed content blocking happens in 59 & 60, the TypeError is unique to 61.

[adamopenweb]

  function e(e) {
    return function (e) {
      function t() {
        i(this, t);
        var e = l(this, (t.__proto__ || Object.getPrototypeOf(t)).call(this));
        return e._properties = {
        },
        e._connected = !1,
        e._createSetters(),
        e._injectStyles(),
        e
      }
      return n(t, e),

[adamopenweb]

OK, if we disable dom.webcomponents.customelements.enabled the bar appears as expected.

[adamopenweb]

Close this for now as a duplicate of: https://bugzilla.mozilla.org/show_bug.cgi?id=1406825

[adamopenweb]

Moved to Bugzilla:
https://bugzilla.mozilla.org/show_bug.cgi?id=1446144