Added missing setPixelRatio() to masking example.

examples/webgl_postprocessing_masking.html

@@ -55,6 +55,7 @@
 
 				renderer = new THREE.WebGLRenderer( { antialias: false } );
 				renderer.setClearColor( 0xe0e0e0 );
+				renderer.setPixelRatio( window.devicePixelRatio );
 				renderer.setSize( window.innerWidth, window.innerHeight );
 				renderer.autoClear = false;
 				document.body.appendChild( renderer.domElement );