as part of `window.utils`, we are setting it on line 78 [https://github.com/mozilla-b2g/gaia/pull/18083/files#diff-d3a7c975537185b803ed902837ef4de5L78] and cleaning it on line 99 [https://github.com/mozilla-b2g/gaia/pull/18083/files#diff-d3a7c975537185b803ed902837ef4de5L99]