In SnapshotReader, changes BackRefNode to be a ValueObject.

runtime/vm/snapshot.h

 // 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.
 
 #ifndef VM_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 275 matching lines @@
   RawGrowableObjectArray* NewGrowableObjectArray();
   RawFloat32x4* NewFloat32x4(float v0, float v1, float v2, float v3);
   RawInt32x4* NewInt32x4(uint32_t v0, uint32_t v1, uint32_t v2, uint32_t v3);
   RawFloat64x2* NewFloat64x2(double v0, double v1);
   RawApiError* NewApiError();
   RawLanguageError* NewLanguageError();
   RawObject* NewInteger(int64_t value);
   RawStacktrace* NewStacktrace();
 
  private:
-  class BackRefNode : public ZoneAllocated {
+  class BackRefNode : public ValueObject {
    public:
     BackRefNode(Object* reference, DeserializeState state)
         : reference_(reference), state_(state) {}
     Object* reference() const { return reference_; }
     bool is_deserialized() const { return state_ == kIsDeserialized; }
     void set_state(DeserializeState state) { state_ = state; }
 
+    BackRefNode& operator=(const BackRefNode& other) {
+      reference_ = other.reference_;
+      state_ = other.state_;
+      return *this;
+    }
+
    private:
     Object* reference_;
     DeserializeState state_;
-
-    DISALLOW_COPY_AND_ASSIGN(BackRefNode);
   };
 
   // Allocate uninitialized objects, this is used when reading a full snapshot.
   RawObject* AllocateUninitialized(const Class& cls, intptr_t size);
 
   RawClass* ReadClassId(intptr_t object_id);
   RawObject* ReadObjectImpl();
   RawObject* ReadObjectImpl(intptr_t header);
   RawObject* ReadObjectRef();
 
@@ skipping 19 matching lines @@
   Array& array_;  // Temporary Array handle.
   Field& field_;  // Temporary Field handle.
   String& str_;  // Temporary String handle.
   Library& library_;  // Temporary library handle.
   AbstractType& type_;  // Temporary type handle.
   TypeArguments& type_arguments_;  // Temporary type argument handle.
   Array& tokens_;  // Temporary tokens handle.
   TokenStream& stream_;  // Temporary token stream handle.
   ExternalTypedData& data_;  // Temporary stream data handle.
   UnhandledException& error_;  // Error handle.
-  GrowableArray<BackRefNode*> backward_references_;
+  GrowableArray<BackRefNode> backward_references_;
 
   friend class ApiError;
   friend class Array;
   friend class BoundedType;
   friend class MixinAppType;
   friend class Class;
   friend class Context;
   friend class ContextScope;
   friend class Field;
   friend class ClosureData;
@@ skipping 276 matching lines @@
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_