Remove unnecessary isolate argument from some visitors

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 12 matching lines @@
   kAllowMarked,
   kRequireMarked
 };
 
 
 class VerifyObjectVisitor : public ObjectVisitor {
  public:
   VerifyObjectVisitor(Isolate* isolate,
                      ObjectSet* allocated_set,
                      MarkExpectation mark_expectation)
-      : ObjectVisitor(isolate),
+      : isolate_(isolate),
         allocated_set_(allocated_set),
         mark_expectation_(mark_expectation) {
   }
 
   virtual void VisitObject(RawObject* obj);
 
  private:
+  Isolate* isolate_;
   ObjectSet* allocated_set_;
   MarkExpectation mark_expectation_;
 
   DISALLOW_COPY_AND_ASSIGN(VerifyObjectVisitor);
 };
 
 // A sample object pointer visitor implementation which verifies that
 // the pointers visited are contained in the isolate heap.
 class VerifyPointersVisitor : public ObjectPointerVisitor {
  public:
@@ skipping 25 matching lines @@
   ObjectPointerVisitor* visitor_;
 
   ObjectSet* allocated_set;
 
   DISALLOW_COPY_AND_ASSIGN(VerifyWeakPointersVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_VERIFIER_H_