Set the default whitespace mode to pre-wrap

sky/tests/widgets/dialog.dart

Index: sky/tests/widgets/dialog.dart
diff --git a/sky/tests/widgets/dialog.dart b/sky/tests/widgets/dialog.dart
index abbc5f08c256f544ab5a6d1da524193a6c8eb172..38f4dca30972d527671148f55969d6686143d0e3 100644
--- a/sky/tests/widgets/dialog.dart
+++ b/sky/tests/widgets/dialog.dart
@@ -13,7 +13,7 @@ main() async {
   await tester.test(() {
     return new Dialog(
       title: new Text("I am a title"),
-      content: new Text("I am some content"),
+      content: new Text("I am some content\nwith a line break"),
       actions: [new Text("I am some actions")]
     );
   });