There are currently users that implement classes (e.g. for mocking
purposes) that implement/extend NativeFieldWrappers and send such
objects across isolates.
This CL ensures such mocks can be sent across isolates again (which was
disabled in breaking change in [0]) as long as mocks do not extend NFW
(and therefore have actual native fields).
In the future the [NativeFieldWrapperClass]s will be marked as `base`
and therefore prevent implementing them, see issue [1].
=> At this point this CL can be reverted again.
[0] https://dart-review.googlesource.com/c/sdk/+/289027
[1] https://github.com/dart-lang/sdk/issues/51896
TEST=adjusted isolate tests
Change-Id: I5fe1110e7046761e3606927063d3ad5e2b4bf4e0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/292320
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
Martin Kustermann
6e252d9793