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

third_party/WebKit/LayoutTests/http/tests/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);
     }
 });