CSSPaint: Move layout tests in csspaint/ to http/tests/csspaint/

third_party/WebKit/LayoutTests/csspaint/resources/paint-logging-green.js

-// Logs the size of the geometry to the console.
-// Fills the context with a green square.
-
-registerPaint('logging-green', class {
-    paint(ctx, geom) {
-        console.log('width: ' + geom.width + ', height: ' + geom.height);
-        ctx.fillStyle = 'green';
-        ctx.fillRect(0, 0, geom.width, geom.height);
-    }
-});