Fix barback test.

pkg/barback/test/barback_mode_test.dart

Index: pkg/barback/test/barback_mode_test.dart
diff --git a/pkg/barback/test/barback_mode_test.dart b/pkg/barback/test/barback_mode_test.dart
index e9fe3932a66a709d1b2df3da258e6086ae6652ce..2d18f09933f50ddf366ea67271e00360cce50ea2 100644
--- a/pkg/barback/test/barback_mode_test.dart
+++ b/pkg/barback/test/barback_mode_test.dart
@@ -11,10 +11,10 @@ import 'utils.dart';
 
 main() {
   initConfig();
-  test("fromString() uses canonical instances for DEBUG and RELEASE", () {
+  test("constructor uses canonical instances for DEBUG and RELEASE", () {
     expect(identical(BarbackMode.DEBUG,
-        new BarbackMode.fromString(BarbackMode.DEBUG.name)), isTrue);
+        new BarbackMode(BarbackMode.DEBUG.name)), isTrue);
     expect(identical(BarbackMode.RELEASE,
-        new BarbackMode.fromString(BarbackMode.RELEASE.name)), isTrue);
+        new BarbackMode(BarbackMode.RELEASE.name)), isTrue);
   });
 }