test: exercise document visibility WebGL screenshots in rendered CI

.github/workflows/e2e.yml

@@ -245,8 +245,9 @@ jobs:
           if grep -l '@headful' "${TEST_FILES[@]}" >/dev/null; then
             E2E_PROJECT_ARGS+=(--project=electron-headful)
           fi
+          node tests/e2e/diagnose-execution-context.mjs
           xvfb-run --auto-servernum bash .github/scripts/e2e-with-window-manager.sh env "${E2E_ENV[@]}" \
-            pnpm run test:e2e "${TEST_FILES[@]}" --workers=1 "${E2E_PROJECT_ARGS[@]}"
+            pnpm run test:e2e "${TEST_FILES[@]}" --workers=1 "${E2E_PROJECT_ARGS[@]}" --repeat-each=5
 
       - name: Upload Playwright traces
         if: failure()

tests/e2e/diagnose-execution-context.mjs

@@ -0,0 +1,10 @@
+import fs from 'node:fs'
+import path from 'node:path'
+import { createRequire } from 'node:module'
+const require = createRequire(import.meta.url)
+const file = path.join(path.dirname(require.resolve('playwright-core/package.json')), 'lib/server/chromium/crExecutionContext.js')
+let source = fs.readFileSync(file, 'utf8')
+const needle = 'function rewriteError(error) {'
+if (!source.includes(needle)) throw new Error('Playwright diagnostic hook missing')
+source = source.replace(needle, needle + '\n  console.error("[raw-context-error]", error.message, error.stack);')
+fs.writeFileSync(file, source)