Ignore errors from transaction rollbacks
Ignore errors from transaction rollbacks

BUG=https://github.com/dart-lang/pub-dartlang-dart/issues/49
R=whesse@google.com

Review URL: https://codereview.chromium.org/1842343002 .

dart-lang/pub-dev,dart-lang/pub-dev,dart-lang/pub-dev,dart-lang/pub-dev