c82c2f9948
This allows the test runner to support context messages, for example the context error messages associated with the new "why not promoted" feature. Bug: https://github.com/dart-lang/sdk/issues/44905 Change-Id: Ie342bde21c43641eafc5d117f328e9fde23c49bc Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/193740 Reviewed-by: Bob Nystrom <rnystrom@google.com> Commit-Queue: Paul Berry <paulberry@google.com>