preserveDrawingBuffer isn't needed anymore.

examples/webgl_performance.html

@@ -77,7 +77,7 @@
 
 				} } );
 
-				renderer = new THREE.WebGLRenderer( { preserveDrawingBuffer: true } );
+				renderer = new THREE.WebGLRenderer();
 				renderer.setSize( window.innerWidth, window.innerHeight );
 				renderer.sortObjects = false;
 				container.appendChild( renderer.domElement );