Fix reference table sorting

Bug: 18638116

(cherry picked from commit 16abc5f28ac9792fd1ba2c82f123cfd871cddbdb)

Change-Id: I15478306b3c2e2bd4f0a1d4307c001f64c0652af
diff --git a/runtime/reference_table.cc b/runtime/reference_table.cc
index 366b1f0..c917d84 100644
--- a/runtime/reference_table.cc
+++ b/runtime/reference_table.cc
@@ -85,7 +85,7 @@
     DCHECK(!runtime->IsClearedJniWeakGlobal(obj2));
     // Sort by class...
     if (obj1->GetClass() != obj2->GetClass()) {
-      return obj1->GetClass()->IdentityHashCode() < obj2->IdentityHashCode();
+      return obj1->GetClass()->IdentityHashCode() < obj2->GetClass()->IdentityHashCode();
     }
     // ...then by size...
     const size_t size1 = obj1->SizeOf();