This replaces all `instanceof` uses for DOM interfaces, since the operator in priviliged context works same as .isInstance(). Differential Revision: https://phabricator.services.mozilla.com/D141785
This replaces all `instanceof` uses for DOM interfaces, since the operator in priviliged context works same as .isInstance(). Differential Revision: https://phabricator.services.mozilla.com/D141785