Remove unused legacyMode from constant transformer
Remove unused legacyMode from constant transformer

Change-Id: I3ccd276d1ebe5aa63d45625da70fd417b93d29c7
Reviewed-on: https://dart-review.googlesource.com/c/94211
Reviewed-by: Kevin Millikin <a6737c91ef81c790d8ad0ae8762bd5b2332a6e42@google.com>

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