browser: fix web vitals test flakiness on Windows (#4630)

* browser: fix web vitals test flakiness on Windows

The TestWebVitalMetricNoInteraction test was failing on Windows due to timing
issues when collecting web vital metrics. This commit:

- Increases timeout from 5s to 10s specifically for Windows
- Adds a 1s delay after page load to ensure metrics are collected
- Uses explicit timeout values instead of DefaultTimeout

These changes make the test more reliable on Windows while maintaining the
same behavior on other platforms.

* Standardize web vital test timeouts

Author: andrewslotin

internal/js/modules/k6/browser/tests/webvital_test.go

@@ -106,7 +106,7 @@ func TestWebVitalMetricNoInteraction(t *testing.T) {
 	)
 
 	done := make(chan struct{})
-	ctx, cancel := context.WithTimeout(browser.context(), 5*time.Second)
+	ctx, cancel := context.WithTimeout(browser.context(), common.DefaultTimeout)
 	defer cancel()
 	go func() {
 		for {
@@ -127,9 +127,9 @@ func TestWebVitalMetricNoInteraction(t *testing.T) {
 		}
 	}()
 
-	// wait until the page is completely loaded.
 	page := browser.NewPage(nil)
 	opts := &common.FrameGotoOptions{
+		// Wait for both load and network idle events
 		WaitUntil: common.LifecycleEventNetworkIdle,
 		Timeout:   common.DefaultTimeout,
 	}
@@ -140,6 +140,9 @@ func TestWebVitalMetricNoInteraction(t *testing.T) {
 	require.NoError(t, err)
 	require.NotNil(t, resp)
 
+	// Add a small delay to ensure all metrics are collected
+	time.Sleep(1 * time.Second)
+
 	// prevents `err:fetching response body: context canceled` warning.`
 	require.NoError(t, page.Close())
 	done <- struct{}{}