Print more info on mark sweep invalid ref crash.

- Add extra info about the field holder.
- Suspend threads when verifying roots.

(cherry pick commit 1e1a47204984e3b72c4a753a2beb704350f38373)

Bug: 20557050
Change-Id: Ia1f2269aaa3b1a81d0594e781e439a5decfb82f9
1 file changed