Fix obsolete comment change in libs document.
Fix obsolete comment change in libs document.

"DateTime.parse taking optional arg".

Change-Id: I67779495a946789ba71ff1dffcdb8089a14f8073
Reviewed-on: https://dart-review.googlesource.com/18182
Reviewed-by: Florian Loitsch <12d47e7a27fad71f0f62618c5962ce04e125ad18@google.com>

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