function onBlur(e) {
      if (!isValidFocusTarget(e.target)) {
        return;
      }

      if (
        e.target.classList.contains('focus-visible') ||
        e.target.hasAttribute('data-focus-visible-added')
      ) {
        // To detect a tab/window switch, we look for a blur event followed
        // rapidly by a visibility change.
        // If we don't see a visibility change within 100ms, it's probably a
        // regular focus change.
        hadFocusVisibleRecently = true;
        window.clearTimeout(hadFocusVisibleRecentlyTimeout);
        hadFocusVisibleRecentlyTimeout = window.setTimeout(function() {
          hadFocusVisibleRecently = false;
        }, 100);
        removeFocusVisibleClass(e.target);
      }
    }
On `blur`, remove the `focus-visible` class from the target.
@param {Event} e