This is not the flag you're looking for.
The 'extension-types' flag was used for an early experiment that is
not directly related to the Extension Types feature currently being
developed. The current feature uses the 'inline-class' flag.
Change-Id: Icbb6c3828c41e743e726161b17da4c7784a2c677
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/316380
Reviewed-by: William Hesse <whesse@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>
