code: function _getSavedBytes(rawFile, compressedFile) {
      var savedBytes = rawFile.size - compressedFile.size;
  
      if (savedBytes > 0) return savedBytes;
  
      return 0;
  }
docs: Returns saved bytes between the raw and compressed files
  @param {File} rawFile
  @param {File} compressedFile
  @returns {Number}