processBuffer( buffer ) {

    		const json = this.json;
    		const buffers = this.buffers;

    		if ( ! json.buffers ) json.buffers = [ { byteLength: 0 } ];

    		// All buffers are merged before export.
    		buffers.push( buffer );

    		return 0;

    	}
Process a buffer to append to the default one.
@param  {ArrayBuffer} buffer
@return {Integer}