1. Provide a framework to traverse persistent prolog weak handles.

runtime/vm/object.cc

 // Copyright (c) 2012, 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 "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 12603 matching lines @@
     const Double& a_double = Double::Cast(*this);
     const Double& b_double = Double::Cast(other);
     if (isnan(a_double.value()) && isnan(b_double.value())) {
       return true;
     }
   }
   return false;
 }
 
 
+intptr_t* Instance::NativeFieldsDataAddr() const {
+  NoGCScope no_gc;
+  RawTypedData* native_fields =
+      reinterpret_cast<RawTypedData*>(*NativeFieldsAddr());
+  if (native_fields == TypedData::null()) {
+    return NULL;
+  }
+  return reinterpret_cast<intptr_t*>(native_fields->ptr()->data_);
+}
+
+
 void Instance::SetNativeField(int index, intptr_t value) const {
   ASSERT(IsValidNativeIndex(index));
   Object& native_fields = Object::Handle(*NativeFieldsAddr());
   if (native_fields.IsNull()) {
     // Allocate backing storage for the native fields.
     native_fields = TypedData::New(kIntPtrCid, NumNativeFields());
     StorePointer(NativeFieldsAddr(), native_fields.raw());
   }
   intptr_t byte_offset = index * sizeof(intptr_t);
   TypedData::Cast(native_fields).SetIntPtr(byte_offset, value);
@@ skipping 5626 matching lines @@
   return "_MirrorReference";
 }
 
 
 void MirrorReference::PrintToJSONStream(JSONStream* stream, bool ref) const {
   Instance::PrintToJSONStream(stream, ref);
 }
 
 
 }  // namespace dart