Don't use TLS for space iterators.

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
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 // or care about intergenerational references. All heap object pointers have to
 // point into the heap to a location that has a map pointer at its first word.
 // Caveat: Heap::Contains is an approximation because it can return true for
 // objects in a heap space but above the allocation pointer.
 class VerifyPointersVisitor: public ObjectVisitor {
  public:
   inline void VisitPointers(Object** start, Object** end);
 };
 
 
-// Space iterator for iterating over all spaces of the heap.
-// Returns each space in turn, and null when it is done.
+// Space iterator for iterating over all spaces of the heap.  Returns each space
+// in turn, and null when it is done.
 class AllSpaces BASE_EMBEDDED {
  public:
+  explicit AllSpaces(Heap* heap) : heap_(heap), counter_(FIRST_SPACE) {}
   Space* next();
-  AllSpaces() { counter_ = FIRST_SPACE; }
  private:
+  Heap* heap_;
   int counter_;
 };
 
 
 // Space iterator for iterating over all old spaces of the heap: Old pointer
-// space, old data space and code space.
-// Returns each space in turn, and null when it is done.
+// space, old data space and code space.  Returns each space in turn, and null
+// when it is done.
 class OldSpaces BASE_EMBEDDED {
  public:
+  explicit OldSpaces(Heap* heap) : heap_(heap), counter_(OLD_POINTER_SPACE) {}
   OldSpace* next();
-  OldSpaces() { counter_ = OLD_POINTER_SPACE; }
  private:
+  Heap* heap_;
   int counter_;
 };
 
 
-// Space iterator for iterating over all the paged spaces of the heap:
-// Map space, old pointer space, old data space, code space and cell space.
-// Returns each space in turn, and null when it is done.
+// Space iterator for iterating over all the paged spaces of the heap: Map
+// space, old pointer space, old data space, code space and cell space.  Returns
+// each space in turn, and null when it is done.
 class PagedSpaces BASE_EMBEDDED {
  public:
+  explicit PagedSpaces(Heap* heap) : heap_(heap), counter_(OLD_POINTER_SPACE) {}
   PagedSpace* next();
-  PagedSpaces() { counter_ = OLD_POINTER_SPACE; }
  private:
+  Heap* heap_;
   int counter_;
 };
 
 
 // Space iterator for iterating over all spaces of the heap.
 // For each space an object iterator is provided. The deallocation of the
 // returned object iterators is handled by the space iterator.
 class SpaceIterator : public Malloced {
  public:
-  SpaceIterator();
-  explicit SpaceIterator(HeapObjectCallback size_func);
+  explicit SpaceIterator(Heap* heap);
+  SpaceIterator(Heap* heap, HeapObjectCallback size_func);
   virtual ~SpaceIterator();
 
   bool has_next();
   ObjectIterator* next();
 
  private:
   ObjectIterator* CreateIterator();
 
+  Heap* heap_;
   int current_space_;  // from enum AllocationSpace.
   ObjectIterator* iterator_;  // object iterator for the current space.
   HeapObjectCallback size_func_;
 };
 
 
 // A HeapIterator provides iteration over the whole heap. It
 // aggregates the specific iterators for the different spaces as
 // these can only iterate over one space only.
 //
 // HeapIterator can skip free list nodes (that is, de-allocated heap
 // objects that still remain in the heap). As implementation of free
 // nodes filtering uses GC marks, it can't be used during MS/MC GC
 // phases. Also, it is forbidden to interrupt iteration in this mode,
 // as this will leave heap objects marked (and thus, unusable).
 class HeapObjectsFilter;
 
 class HeapIterator BASE_EMBEDDED {
  public:
   enum HeapObjectsFiltering {
     kNoFiltering,
     kFilterUnreachable
   };
 
-  HeapIterator();
-  explicit HeapIterator(HeapObjectsFiltering filtering);
+  explicit HeapIterator(Heap* heap);
+  HeapIterator(Heap* heap, HeapObjectsFiltering filtering);
   ~HeapIterator();
 
   HeapObject* next();
   void reset();
 
  private:
   // Perform the initialization.
   void Init();
   // Perform all necessary shutdown (destruction) work.
   void Shutdown();
   HeapObject* NextObject();
 
+  Heap* heap_;
   HeapObjectsFiltering filtering_;
   HeapObjectsFilter* filter_;
   // Space iterator for iterating all the spaces.
   SpaceIterator* space_iterator_;
   // Object iterator for the space currently being iterated.
   ObjectIterator* object_iterator_;
 };
 
 
 // Cache for mapping (map, property name) into field offset.
@@ skipping 500 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_