[Isolates] Get the current heap from page header instead of Map field.

src/serialize.cc

 // 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 695 matching lines @@
                               Object** write_back) {
   int size = source_->GetInt() << kObjectAlignmentBits;
   Address address = Allocate(space_number, space, size);
   *write_back = HeapObject::FromAddress(address);
   Object** current = reinterpret_cast<Object**>(address);
   Object** limit = current + (size >> kPointerSizeLog2);
   if (FLAG_log_snapshot_positions) {
     LOG(SnapshotPositionEvent(address, source_->position()));
   }
   ReadChunk(current, limit, space_number, address);
-
-  if (space_number == MAP_SPACE) {
-    ASSERT(size == Map::kSize);
-    HeapObject* obj = HeapObject::FromAddress(address);
-    Map* map = reinterpret_cast<Map*>(obj);
-    map->set_heap(isolate_->heap());
-  }
 }
 
 
 // This macro is always used with a constant argument so it should all fold
 // away to almost nothing in the generated code.  It might be nicer to do this
 // with the ternary operator but there are type issues with that.
 #define ASSIGN_DEST_SPACE(space_number)                                        \
   Space* dest_space;                                                           \
   if (space_number == NEW_SPACE) {                                             \
     dest_space = isolate->heap()->new_space();                                \
@@ skipping 804 matching lines @@
       fullness_[space] = RoundUp(fullness_[space], Page::kPageSize);
     }
   }
   int allocation_address = fullness_[space];
   fullness_[space] = allocation_address + size;
   return allocation_address;
 }
 
 
 } }  // namespace v8::internal