Allow creating non-thread-local Persistents that can be passed between threads.

Source/heap/Heap.h

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 47 matching lines @@
 
 const size_t markBitMask = 1;
 const size_t freeListMask = 2;
 const size_t debugBitMask = 4;
 const size_t sizeMask = ~7;
 const uint8_t freelistZapValue = 42;
 const uint8_t finalizedZapValue = 24;
 
 class HeapStats;
 class PageMemory;
-template<typename T> class Persistent;
+template<ThreadAffinity affinity> class ThreadLocalPersistents;
+template<typename T, typename RootsAccessor = ThreadLocalPersistents<ThreadingTrait<T>::Affinity > > class Persistent;
 
 HEAP_EXPORT size_t osPageSize();
 
 // Blink heap pages are set up with a guard page before and after the
 // payload.
 inline size_t blinkPagePayloadSize()
 {
     return blinkPageSize - 2 * osPageSize();
 }
 
@@ skipping 1589 matching lines @@
 // to export. This forces it to export all the methods from ThreadHeap.
 template<> void ThreadHeap<FinalizedHeapObjectHeader>::addPageToHeap(const GCInfo*);
 template<> void ThreadHeap<HeapObjectHeader>::addPageToHeap(const GCInfo*);
 extern template class HEAP_EXPORT ThreadHeap<FinalizedHeapObjectHeader>;
 extern template class HEAP_EXPORT ThreadHeap<HeapObjectHeader>;
 #endif
 
 }
 
 #endif // Heap_h