Put metadata fields in their owner class.

runtime/vm/class_finalizer.cc

Index: runtime/vm/class_finalizer.cc
diff --git a/runtime/vm/class_finalizer.cc b/runtime/vm/class_finalizer.cc
index 9e90e410515ed048e2e481eb1ff739f91e3d5c29..ea6303aeabfd10da15191a9677a9574e5da9a4e5 100644
--- a/runtime/vm/class_finalizer.cc
+++ b/runtime/vm/class_finalizer.cc
@@ -2146,7 +2146,7 @@ void ClassFinalizer::ApplyMixinMembers(const Class& cls) {
   // Now clone the fields from the mixin class. There should be no
   // existing fields in the mixin application class.
   ASSERT(Array::Handle(cls.fields()).Length() == 0);
-  Array& fields = Array::Handle(isolate, mixin_cls.fields());
+  const Array& fields = Array::Handle(isolate, mixin_cls.fields());
   Field& field = Field::Handle(isolate);
   const GrowableObjectArray& cloned_fields =
       GrowableObjectArray::Handle(isolate, GrowableObjectArray::New());
@@ -2158,8 +2158,7 @@ void ClassFinalizer::ApplyMixinMembers(const Class& cls) {
       cloned_fields.Add(field);
     }
   }
-  fields = Array::MakeArray(cloned_fields);
-  cls.SetFields(fields);
+  cls.AddFields(cloned_fields);
 
   if (FLAG_trace_class_finalization) {
     OS::Print("Done applying mixin members of %s to %s\n",
@@ -2289,7 +2288,6 @@ void ClassFinalizer::FinalizeTypesInClass(const Class& cls) {
     // This class should not contain any fields or functions yet, because it has

[Ivan Posva, 2014/05/08 05:18:50]

Please update the comment. Especially since it appears that this class now can
already contain fields when we get here.

[rmacnak, 2014/05/08 18:14:54]

Noted the class might contain metadata fields for type parameters.

     // not been compiled yet. Since 'ResolveAndFinalizeMemberTypes(cls)' has not
     // been called yet, unfinalized member types could choke the snapshotter.
-    ASSERT(Array::Handle(cls.fields()).Length() == 0);
     ASSERT(Array::Handle(cls.functions()).Length() == 0);
   }
 }