Fix ast_builder.status
Fix ast_builder.status

This should fix a breakage in buildbots such as
https://build.chromium.org/p/client.dart/builders/vm-kernel-linux-release-x64-be
Change-Id: Idcdcdf841bab60b83675872a2ece385e2f4fd3b7
Reviewed-on: https://dart-review.googlesource.com/25513
Reviewed-by: Paul Berry <72d414e3a99fb120308437779d51667bcc0984eb@google.com>

dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk