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

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
@@ skipping 3041 matching lines @@
   DARTSCOPE(isolate);
   CHECK_CALLBACK_STATE(isolate);
 
   const Type& type_obj = Api::UnwrapTypeHandle(isolate, type);
   // Get the class to instantiate.
   if (type_obj.IsNull()) {
     RETURN_TYPE_ERROR(isolate, type, Type);
   }
   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_fields_marked_nullable()) {
+    // 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_fields_marked_nullable();
+      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));
 }
 
 
 static Dart_Handle SetupArguments(Isolate* isolate,
                                   int num_args,
                                   Dart_Handle* arguments,
                                   int extra_args,
                                   Array* args) {
@@ skipping 1443 matching lines @@
 }
 
 
 // --- Service support ---
 
 DART_EXPORT Dart_Isolate Dart_GetServiceIsolate(void* callback_data) {
   return Api::CastIsolate(Service::GetServiceIsolate(callback_data));
 }
 
 }  // namespace dart