Add a UpdatedGuardedCidBit to Class object so that we don't have

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
===================================================================
--- runtime/vm/dart_api_impl.cc	(revision 32267)
+++ runtime/vm/dart_api_impl.cc	(working copy)
@@ -3059,21 +3059,25 @@
   }
   const Class& cls = Class::Handle(isolate, type_obj.type_class());
 
-  // Mark all fields as nullable.
-  Class& iterate_cls = Class::Handle(isolate, cls.raw());
-  Field& field = Field::Handle(isolate);
-  Array& fields = Array::Handle(isolate);
-  while (!iterate_cls.IsNull()) {
-    fields = iterate_cls.fields();
-    iterate_cls = iterate_cls.SuperClass();
-    for (int field_num = 0; field_num < fields.Length(); field_num++) {
-      field ^= fields.At(field_num);
-      if (field.is_static()) {
-        continue;
+  if (!cls.is_updated_guarded_cid()) {

[srdjan, 2014/02/04 00:36:55]

Change the name as discussed offline (something a la
all_fields_marked_as_nullable)

[siva, 2014/02/04 00:52:25]

Done.

+    // Mark all fields as nullable.
+    Class& iterate_cls = Class::Handle(isolate, cls.raw());
+    Field& field = Field::Handle(isolate);
+    Array& fields = Array::Handle(isolate);
+    while (!iterate_cls.IsNull()) {
+      iterate_cls.set_is_updated_guarded_cid();
+      fields = iterate_cls.fields();
+      iterate_cls = iterate_cls.SuperClass();
+      for (int field_num = 0; field_num < fields.Length(); field_num++) {
+        field ^= fields.At(field_num);
+        if (field.is_static()) {
+          continue;
+        }
+        field.UpdateGuardedCidAndLength(Object::null_object());
       }
-      field.UpdateGuardedCidAndLength(Object::null_object());
     }
   }
+
   // Allocate an object for the given class.
   return Api::NewHandle(isolate, Instance::New(cls));
 }