Tangents are not needed, this was just copy-paste relict.

examples/webgl_materials_bumpmap.html

@@ -200,8 +200,6 @@
 
 			function createScene( geometry, scale, material ) {
 
-				geometry.computeTangents();
-
 				mesh = new THREE.Mesh( geometry, material );
 
 				mesh.position.y = - 50;