Calculates retaining paths through user fields and ignores VM objects

runtime/vm/object_graph.h

 // Copyright (c) 2014, 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 RUNTIME_VM_OBJECT_GRAPH_H_
 #define RUNTIME_VM_OBJECT_GRAPH_H_
 
 #include "vm/allocation.h"
 
 namespace dart {
@@ skipping 45 matching lines @@
     // trigger GC in any way.
     virtual Direction VisitObject(StackIterator* it) = 0;
   };
 
   explicit ObjectGraph(Thread* thread);
   ~ObjectGraph();
 
   // Visits all strongly reachable objects in the isolate's heap, in a
   // pre-order, depth first traversal.
   void IterateObjects(Visitor* visitor);
+  void IterateUserObjects(Visitor* visitor);
 
   // Like 'IterateObjects', but restricted to objects reachable from 'root'
   // (including 'root' itself).
   void IterateObjectsFrom(const Object& root, Visitor* visitor);
   void IterateObjectsFrom(intptr_t class_id, Visitor* visitor);
 
   // The number of bytes retained by 'obj'.
   intptr_t SizeRetainedByInstance(const Object& obj);
   intptr_t SizeReachableByInstance(const Object& obj);
 
@@ skipping 31 matching lines @@
                      SnapshotRoots roots,
                      bool collect_garbage);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ObjectGraph);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_OBJECT_GRAPH_H_