trezor-firmware/emscripten/pre.js

// stub importScripts for the faulty detection of web worker env
if (typeof importScripts === 'undefined'
    && typeof WorkerGlobalScope !== 'undefined'
    && this instanceof WorkerGlobalScope
   ) {
       this.importScripts = function () {
           throw new Error('importScripts is a stub');
       };
   }