cmd: remove js runtime workaround

The js/wasm bug meant that printing to stdout in the e2e app would crash
the runtime, so we couldn't synchronize with the app like in the other
drivers.

Now that the bug is fixed, we can do the same as the other drivers just
fine.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>

cmd/gogio/js_test.go

@@ -15,7 +15,6 @@ import (
 	"os/exec"
 	"strings"
 	"testing"
-	"time"
 
 	"github.com/chromedp/cdproto/runtime"
 	"github.com/chromedp/chromedp"
@@ -26,11 +25,14 @@ import (
 type JSTestDriver struct {
 	t *testing.T
 
+	frameNotifs chan bool
+
 	// ctx is the chromedp context.
 	ctx context.Context
 }
 
 func (d *JSTestDriver) Start(t_ *testing.T, path string, width, height int) {
+	d.frameNotifs = make(chan bool, 1)
 	d.t = t_
 
 	if raceEnabled {
@@ -92,6 +94,14 @@ func (d *JSTestDriver) Start(t_ *testing.T, path string, width, height int) {
 	chromedp.ListenTarget(ctx, func(ev interface{}) {
 		switch ev := ev.(type) {
 		case *runtime.EventConsoleAPICalled:
+			if ev.Type == "log" && len(ev.Args) == 1 &&
+				// Note that the argument values are JSON.
+				string(ev.Args[0].Value) == `"frame ready"` {
+
+				d.frameNotifs <- true
+				// These logs are expected. Don't show them.
+				break
+			}
 			switch ev.Type {
 			case "log", "info", "warning", "error":
 				var args strings.Builder
@@ -123,8 +133,9 @@ func (d *JSTestDriver) Start(t_ *testing.T, path string, width, height int) {
 	); err != nil {
 		d.t.Fatal(err)
 	}
-	// TODO(mvdan): synchronize with the app instead
-	time.Sleep(200 * time.Millisecond)
+
+	// Wait for the gio app to render.
+	<-d.frameNotifs
 }
 
 func (d *JSTestDriver) Screenshot() image.Image {
@@ -147,6 +158,7 @@ func (d *JSTestDriver) Click(x, y int) {
 	); err != nil {
 		d.t.Fatal(err)
 	}
-	// TODO(mvdan): synchronize with the app instead
-	time.Sleep(200 * time.Millisecond)
+
+	// Wait for the gio app to render after this click.
+	<-d.frameNotifs
 }

cmd/gogio/testdata/red.go

@@ -8,7 +8,6 @@ import (
 	"image"
 	"image/color"
 	"log"
-	"runtime"
 
 	"gioui.org/app"
 	"gioui.org/f32"
@@ -82,13 +81,6 @@ func loop(w *app.Window) error {
 
 			e.Frame(gtx.Ops)
 
-			if runtime.GOOS == "js" {
-				// TODO(mvdan): Unfortunately, printing to
-				// stdout crashes the js/wasm port. Use the
-				// prints once the issue is fixed:
-				// https://github.com/golang/go/issues/35256
-				break
-			}
 			switch notify {
 			case notifyInvalidate:
 				notify = notifyPrint