static deleteAll_() {
    const name = shaka.offline.indexeddb.StorageMechanism.DB_NAME;

    const p = new shaka.util.PublicPromise();

    const del = window.indexedDB.deleteDatabase(name);
    del.onblocked = (event) => {
      shaka.log.warning('Deleting', name, 'is being blocked', event);
    };
    del.onsuccess = (event) => {
      p.resolve();
    };
    del.onerror = (event) => {
      p.reject(new shaka.util.Error(
          shaka.util.Error.Severity.CRITICAL,
          shaka.util.Error.Category.STORAGE,
          shaka.util.Error.Code.INDEXED_DB_ERROR,
          del.error));

      // Firefox will raise an error on the main thread unless we stop it here.
      event.preventDefault();
    };

    return p;
  }
Delete the indexed db instance so that all stores are deleted and cleared.
This will force the database to a like-new state next time it opens.

@return {!Promise}
@private