Daniel Andersson
7d82391e89
Unsynchronized access to the contents of another thread is dangerous, even for just ASSERTs, as shown by issue 23958. Verify the bidirectional Isolate<->Thread pointer invariant when *setting* the mutator_thread_ field, and limit the interface to comparisons with NULL and the current thread. BUG=https://github.com/dart-lang/sdk/issues/23958 R=johnmccutchan@google.com Review URL: https://codereview.chromium.org//1260283007 .