6ef967fb07
Enum forwarding requires evaluating and canonicalizing the new enum instances. If these in turn refer to other instances of classes with shape changes, canonicalization may try to compare instances of the old and new shapes and dereference past the end of an object. By waiting for instance morphing to complete, canonicalization can only see instances with the new shape.
Also, don't attempt to forward Enum.values. When an enum member is added or removed, this has the same merging problem as 40442.
Cf. bad074cc49.
TEST=ci
Bug: https://github.com/flutter/flutter/issues/129177
Change-Id: I19d0508059bade8496000eeea257bb0730f11d17
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/316041
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>