Disallow expressions statements starting with `{`.
Disallow expressions statements starting with `{`.

The current specification only prohibits expressions statements where the
expression *is* a map, not those that *start with* a map.
Implementations have always rejected those starting with a map.

Bug: http://dartbug.com/725
Change-Id: I805a6f82d1afdcf335aff73e74dac1f14e5a6afe
Reviewed-on: https://dart-review.googlesource.com/71247
Commit-Queue: Lasse R.H. Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>
Reviewed-by: Erik Ernst <251bb01623bfda2cd9151e339a6e783ca432874c@google.com>

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