2a475cfe9e
Adjust Dart.g and Dart.g4 to align them with the augmentations feature specification and the language specification. In particular, the handling of the keyword AUGMENT is simplified, and `topLevelDefinition` is renamed. Change-Id: I99dc5c6e5e3135eae14f49587d60c530e303f0e3 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/476401 Reviewed-by: Chloe Stefantsova <cstefantsova@google.com> Commit-Queue: Chloe Stefantsova <cstefantsova@google.com> Auto-Submit: Erik Ernst <eernst@google.com>