Simplify visitor marking mode tracking.

third_party/WebKit/Source/platform/heap/MarkingVisitor.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MarkingVisitor_h
 #define MarkingVisitor_h
 
 #include "platform/heap/MarkingVisitorImpl.h"
 
 namespace blink {
 
 class MarkingVisitor final : public Visitor,
                              public MarkingVisitorImpl<MarkingVisitor> {
  public:
   using Impl = MarkingVisitorImpl<MarkingVisitor>;
 
-  MarkingVisitor(ThreadState* state, Visitor::MarkingMode mode)
+  MarkingVisitor(ThreadState* state, VisitorMarkingMode mode)
       : Visitor(state, mode) {}
 
   void markHeader(HeapObjectHeader* header, TraceCallback callback) override {
     Impl::markHeader(header, header->payload(), callback);
   }
 
   void mark(const void* objectPointer, TraceCallback callback) override {
     Impl::mark(objectPointer, callback);
   }
 
@@ skipping 35 matching lines @@
 
   void registerWeakCellWithCallback(void** cell,
                                     WeakCallback callback) override {
     Impl::registerWeakCellWithCallback(cell, callback);
   }
 };
 
 }  // namespace blink
 
 #endif