Add the "- waiting on"/"- waiting to lock" lines to the SIGQUIT output.

Change-Id: I0a8ab2e9e54c390e0d499ef464d82c2f2c628cbe
diff --git a/src/thread_list.h b/src/thread_list.h
index e5d9eab..35b23e7 100644
--- a/src/thread_list.h
+++ b/src/thread_list.h
@@ -87,12 +87,10 @@
       // Try to get it from TLS.
       self = Thread::Current();
     }
+    // self may still be NULL during VM shutdown.
     Thread::State old_state;
     if (self != NULL) {
       old_state = self->SetState(Thread::kVmWait);
-    } else {
-      // This happens during VM shutdown.
-      old_state = Thread::kUnknown;
     }
     Runtime::Current()->GetThreadList()->thread_list_lock_.Lock();
     if (self != NULL) {