fix for retina screens (#9138)

examples/webgl_gpgpu_water.html

@@ -480,7 +480,7 @@
 
 			function setMouseCoords( x, y ) {
 
-				mouseCoords.set( ( x / renderer.domElement.width ) * 2 - 1, - ( y / renderer.domElement.height ) * 2 + 1 );
+				mouseCoords.set( ( x / renderer.domElement.clientWidth ) * 2 - 1, - ( y / renderer.domElement.clientHeight ) * 2 + 1 );
 				mouseMoved = true;
 
 			}