Remove now-unused Visitor::m_isGlobalMarkingVisitor field.

third_party/WebKit/Source/platform/heap/TraceTraits.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 TraceTraits_h
 #define TraceTraits_h
 
 #include "platform/heap/GCInfo.h"
 #include "platform/heap/Heap.h"
 #include "platform/heap/InlinedGlobalMarkingVisitor.h"
+#include "platform/heap/StackFrameDepth.h"
 #include "platform/heap/Visitor.h"
 #include "wtf/Allocator.h"
 #include "wtf/Assertions.h"
 #include "wtf/Deque.h"
 #include "wtf/HashCountedSet.h"
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/HashTable.h"
 #include "wtf/LinkedHashSet.h"
 #include "wtf/ListHashSet.h"
@@ skipping 564 matching lines @@
         // since iterating over the hash table backing will find the whole
         // chain.
         visitor->markNoTracing(node);
         return false;
     }
 };
 
 } // namespace WTF
 
 #endif