Method waitFor_

src/service/extensions-impl.js:576–590

* Creates or returns an existing promise that will yield as soon as the * extension has been loaded. * @param {!ExtensionHolderDef} holder * @return {!Promise<!ExtensionDef>} * @private

(holder)

   * @private
   */
  waitFor_(holder) {
    if (!holder.promise) {
      if (holder.loaded) {
        holder.promise = Promise.resolve(holder.extension);
      } else if (holder.error) {
        holder.promise = Promise.reject(holder.error);
      } else {
        const deferred = new Deferred();
        holder.promise = deferred.promise;
        holder.resolve = deferred.resolve;
        holder.reject = deferred.reject;
      }
    }
    return holder.promise;
  }

  /**
   * Ensures that the script has already been injected in the page.