Restore frame validation (fixes to CL faaf60801f72).

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index e0f8752c1d1ec4c1c163e4bcfd46bf6fec605b11..10873ae03c37990f98114808b4acab3361a9455b 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -1627,8 +1627,8 @@ void Isolate::VisitObjectPointers(ObjectPointerVisitor* visitor,
     deopt_context()->VisitObjectPointers(visitor);
   }
 
-  // Visit objects in thread registry (e.g., handles in zones).
-  thread_registry()->VisitObjectPointers(visitor);
+  // Visit objects in thread registry (e.g., Dart stack, handles in zones).
+  thread_registry()->VisitObjectPointers(visitor, validate_frames);
 }