Expandos collide after a hot restart. This currently fails because
the DDC implementation uses a static field (_keyCounter) to compute a
unique name for each expando. After a hot-restart the counter gets reset
and keys get reused accidentally.
A hacky fix would be to ensure this field is not reset after restarts,
but a more robust fix would be to use a weak map implementation like
dart2js does.
Change-Id: I991874aabf836be66cbd44de07dd38e681415ae7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/199221
Reviewed-by: Nicholas Shahan <nshahan@google.com>
