Remove now-unused Visitor::m_isGlobalMarkingVisitor field.

third_party/WebKit/Source/platform/heap/HeapAllocator.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 HeapAllocator_h
 #define HeapAllocator_h
 
 #include "platform/heap/Heap.h"
 #include "platform/heap/TraceTraits.h"
 #include "wtf/Allocator.h"
 #include "wtf/Assertions.h"
-#include "wtf/Atomics.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"
 #include "wtf/TypeTraits.h"
 #include "wtf/Vector.h"
 
@@ skipping 532 matching lines @@
     static_assert(sizeof(T), "T must be fully defined");
     // All heap allocated node pointers need visiting to keep the nodes alive,
     // regardless of whether they contain pointers to other heap allocated
     // objects.
     static const bool value = true;
 };
 
 } // namespace WTF
 
 #endif