fix hmr test errors

go/jsbundler/hmr_browser_test.go

@@ -82,7 +82,7 @@ setTimeout(() => {
 }, 0);
 `)
 
-	eps, err := loadVendorManifest(filepath.Join(frontendAbs, "vendor"))
+	eps, err := loadVendorManifest([]string{filepath.Join(frontendAbs, "vendor")})
 	if err != nil {
 		t.Fatalf("vendor manifest: %v", err)
 	}
@@ -90,7 +90,7 @@ setTimeout(() => {
 		hub:               newHub(),
 		frontend:          frontendAbs,
 		srcRoot:           tmpSrc,
-		vendor:            filepath.Join(frontendAbs, "vendor"),
+		vendorDirs:        []string{filepath.Join(frontendAbs, "vendor")},
 		graph:             newModuleGraph(),
 		vendorCache:       map[string][]byte{},
 		cssTrigger:        make(chan struct{}, 1),