[Isolates] Add a pointer to Heap to a meta map.

src/heap-inl.h

 // Copyright 2006-2008 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
@@ skipping 363 matching lines @@
   }
   ASSERT(amount_of_external_allocated_memory_ >= 0);
   return amount_of_external_allocated_memory_;
 }
 
 
 void Heap::SetLastScriptId(Object* last_script_id) {
   roots_[kLastScriptIdRootIndex] = last_script_id;
 }
 
+Isolate* Heap::isolate() {
+  return reinterpret_cast<Isolate*>(reinterpret_cast<intptr_t>(this) -
+      reinterpret_cast<size_t>(reinterpret_cast<Isolate*>(4)->heap()) + 4);
+}
 
 #define GC_GREEDY_CHECK() \
   ASSERT(!FLAG_gc_greedy || HEAP->GarbageCollectionGreedyCheck())
 
 
 // Calls the FUNCTION_CALL function and retries it up to three times
 // to guarantee that any allocations performed during the call will
 // succeed if there's enough memory.
 
 // Warning: Do not use the identifiers __object__ or __scope__ in a
@@ skipping 169 matching lines @@
 #ifdef DEBUG
   UpdateLiveObjectCount(obj);
 #endif
   obj->SetMark();
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_