isImage() {
    var isImage = this.types.some((type) => {
      // Firefox will have a type of application/x-moz-file for images during
      // dragging
      return type.indexOf('application/x-moz-file') != -1;
    });

    if (isImage) {
      return true;
    }

    var items = this.getFiles();
    for (var i = 0; i < items.length; i++) {
      var type = items[i].type;
      if (!PhotosMimeType.isImage(type)) {
        return false;
      }
    }

    return true;
  }
Is this an image data transfer?

@return {boolean}