627e89639c
Verify expected state of mark bit, depending on: - pre vs. post-GC - VM vs. regular isolate - concurrent vs. regular sweep Review URL: https://codereview.chromium.org//630933002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@40943 260f80e4-7a28-3924-810f-c04153c831b5