Added setPixelRatio() to RollerCoaster example.

examples/webvr_rollercoaster.html

@@ -34,6 +34,7 @@
 
 			var renderer = new THREE.WebGLRenderer( { antialias: true } );
 			renderer.setClearColor( 0xf0f0ff );
+			renderer.setPixelRatio( window.devicePixelRatio );
 			renderer.setSize( window.innerWidth, window.innerHeight );
 			document.body.appendChild( renderer.domElement );