code: function createImportPromise(loader, name, promise) {
      var importPromises = loader._loader.importPromises;
      return importPromises[name] = promise.then(function(m) {
        importPromises[name] = undefined;
        return m;
      }, function(e) {
        importPromises[name] = undefined;
        throw e;
      });
    }
docs: 26.3.1.1 defined at top importPromises adds ability to import a module twice without error - https://bugs.ecmascript.org/show_bug.cgi?id=2601