code: function GLTFDracoMeshCompressionExtension( json, dracoLoader ) {
  
    if ( !dracoLoader ) {
  
      throw new Error( 'THREE.GLTFLoader: No DRACOLoader instance provided.' );
  
    }
  
    this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
    this.json = json;
    this.dracoLoader = dracoLoader;
    THREE.DRACOLoader.getDecoderModule();
  
  }
docs: DRACO Mesh Compression Extension
  
  Specification: https://github.com/KhronosGroup/glTF/pull/874