code: function findByURL (files, url) {
    for (var i = 0; i < files.length; i++) {
      var file = files[i];
      if (file.url === url) {
        return file;
      }
    }
  }
docs: Finds a file by its exact URL
  
  @param {FileArray} files
  @param {string} url
  @returns {?File}