[vm] Ensure class is type finalized before looking members in it up
[vm] Ensure class is type finalized before looking members in it up

Fixes https://github.com/dart-lang/sdk/issues/43369

Change-Id: I6f181e0a544faf723db86c07649843e895e6ad58
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/162189
Reviewed-by: Tess Strickland <cce218d042444252b7ac446d60910fca7732559c@google.com>
Commit-Queue: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk