code: function fixHiddenIFrames() {
      function checkIFrames() {
        function checkIFrame(settingId) {
          function chkDimension(dimension) {
            return (
              '0px' ===
              (settings[settingId] && settings[settingId].iframe.style[dimension])
            )
          }
  
          function isVisible(el) {
            return null !== el.offsetParent
          }
  
          if (
            settings[settingId] &&
            isVisible(settings[settingId].iframe) &&
            (chkDimension('height') || chkDimension('width'))
          ) {
            trigger(
              'Visibility change',
              'resize',
              settings[settingId].iframe,
              settingId
            )
          }
        }
  
        Object.keys(settings).forEach(function(key) {
          checkIFrame(settings[key])
        })
      }
  
      function mutationObserved(mutations) {
        log(
          'window',
          'Mutation observed: ' + mutations[0].target + ' ' + mutations[0].type
        )
        debouce(checkIFrames, 16)
      }
  
      function createMutationObserver() {
        var target = document.querySelector('body'),
          config = {
            attributes: true,
            attributeOldValue: false,
            characterData: true,
            characterDataOldValue: false,
            childList: true,
            subtree: true
          },
          observer = new MutationObserver(mutationObserved)
  
        observer.observe(target, config)
      }
  
      var MutationObserver = getMutationObserver()
      if (MutationObserver) {
        createMutationObserver()
      }
    }
docs: Not testable in PhantomJS /* istanbul ignore next