Revert "Rely on upstream timeout"

This reverts commit f7f0c8c470.

ui/preview.js

@@ -65,6 +65,9 @@ export class Preview extends Component {
       canvasHolder
     );
 
+    // I have no idea why, but if we connect too soon, it just hangs...
+    await new Promise(resolve => setTimeout(resolve, 1000));
+
     while (this.canvasRef.current) {
       try {
         let blob = await this.props.getPreview();