[Isolates] Add heap pointer to all maps and use map->heap() more.

src/objects-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 1054 matching lines @@
 }
 #endif
 
 
 Heap* HeapObject::GetHeap() {
   // During GC, the map pointer in HeapObject is used in various ways that
   // prevent us from retrieving Heap from the map.
   // Assert that we are not in GC, implement GC code in a way that it doesn't
   // pull heap from the map.
   ASSERT(HEAP->is_safe_to_read_maps());
-  return map()->map()->heap();
+  return map()->heap();
 }
 
 
 Map* HeapObject::map() {
   return map_word().ToMap();
 }
 
 
 void HeapObject::set_map(Map* value) {
   set_map_word(MapWord::FromMap(value));
@@ skipping 1382 matching lines @@
   // GetCodeFromTargetAddress might be called when marking objects during mark
   // sweep. reinterpret_cast is therefore used instead of the more appropriate
   // Code::cast. Code::cast does not work when the object's map is
   // marked.
   Code* result = reinterpret_cast<Code*>(code);
   return result;
 }
 
 
 Heap* Map::heap() {
-  ASSERT(instance_type() == MAP_TYPE);
-  ASSERT(this == map());
   Heap* heap = reinterpret_cast<Heap*>(READ_INTPTR_FIELD(this, kHeapOffset));
   ASSERT(heap != NULL);
   ASSERT(heap->isolate() == Isolate::Current());
   return heap;
 }
 
 
 void Map::set_heap(Heap* heap) {
   ASSERT(heap != NULL);
   ASSERT(heap->isolate() == Isolate::Current());
@@ skipping 1072 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_