- Add extra checking when validating objects.

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"
 #include "vm/visitor.h"
 
 namespace dart {
 
 DECLARE_FLAG(bool, verify_on_transition);
 
 #define VERIFY_ON_TRANSITION                                                   \
   if (FLAG_verify_on_transition) {                                             \
     VerifyPointersVisitor::VerifyPointers();                                   \
     Isolate::Current()->heap()->Verify();                                      \
   }                                                                            \
 
 
 // Forward declarations.
+class Isolate;
 class RawObject;
 
 // A sample object pointer visitor implementation which verifies that
 // the pointers visited are contained in the isolate heap.
 class VerifyPointersVisitor : public ObjectPointerVisitor {
  public:
-  VerifyPointersVisitor() {}
+  explicit VerifyPointersVisitor(Isolate* isolate) : isolate_(isolate) {}
 
   virtual void VisitPointers(RawObject** first, RawObject** last);
 
   static void VerifyPointers();
 
  private:
+  Isolate* isolate_;
+
   DISALLOW_COPY_AND_ASSIGN(VerifyPointersVisitor);
 };
 
 class VerifyWeakPointersVisitor : public HandleVisitor {
  public:
   explicit VerifyWeakPointersVisitor(VerifyPointersVisitor* visitor)
       : visitor_(visitor) {
   }
 
   virtual void VisitHandle(uword addr);
 
  private:
   ObjectPointerVisitor* visitor_;
 
   DISALLOW_COPY_AND_ASSIGN(VerifyWeakPointersVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_VERIFIER_H_