function loadDriveApi() {
    if (!wtf.io.drive.downloadFileLoadResult_) {
      wtf.io.drive.downloadFileLoadResult_ = new goog.result.SimpleResult();
      gapi.client.load('drive', 'v2', function() {
        wtf.io.drive.downloadFileLoadResult_.setValue(true);
      });
    }
    goog.result.wait(wtf.io.drive.downloadFileLoadResult_, getMetadata);
  }
Begins querying a file from Drive.
@param {string} fileId Drive file ID.
@return {!goog.result.Result} Async result. The value will be a
    {@see wtf.io.drive.DriveFile} object.