Use a tag bit for indicating prologue weak persistent handles, this avoids

runtime/vm/verifier.h

 // Copyright (c) 2011, 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_VERIFIER_H_
 #define VM_VERIFIER_H_
 
 #include "vm/flags.h"
 #include "vm/globals.h"
 #include "vm/handles.h"
@@ skipping 39 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(VerifyPointersVisitor);
 };
 
 class VerifyWeakPointersVisitor : public HandleVisitor {
  public:
   explicit VerifyWeakPointersVisitor(VerifyPointersVisitor* visitor)
       : visitor_(visitor) {
   }
 
-  virtual void VisitHandle(uword addr);
+  virtual void VisitHandle(uword addr, bool is_prologue_weak);
 
  private:
   ObjectPointerVisitor* visitor_;
 
   ObjectSet* allocated_set;
 
   DISALLOW_COPY_AND_ASSIGN(VerifyWeakPointersVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_VERIFIER_H_