Make the RuntimeTest use Runtime instances instead of its constituents.

Change-Id: I1005f279259917ff07d24e3bcd3643992ec8e3bd
diff --git a/src/thread.cc b/src/thread.cc
index 56eeb7f..c2483c0 100644
--- a/src/thread.cc
+++ b/src/thread.cc
@@ -156,7 +156,10 @@
   // Make sure that all threads have exited and unregistered when we
   // reach this point. This means that all daemon threads had been
   // shutdown cleanly.
-  CHECK_EQ(list_.size(), 0U);
+  CHECK_EQ(list_.size(), 1U);
+  // TODO: wait for all other threads to unregister
+  CHECK_EQ(list_.front(), Thread::Current());
+  // TODO: detach the current thread
   delete lock_;
   lock_ = NULL;
 }