Create a separate space for global property cells

src/serialize.h

Index: src/serialize.h
===================================================================
--- src/serialize.h	(revision 2321)
+++ src/serialize.h	(working copy)
@@ -321,6 +321,8 @@
 
   // Resolve caches the following:
   List<Page*> map_pages_;          // All pages in the map space.
+  // All pages in the global property cell space.
+  List<Page*> global_property_cell_pages_;
   List<Page*> old_pointer_pages_;  // All pages in the old pointer space.
   List<Page*> old_data_pages_;     // All pages in the old data space.
   List<Page*> code_pages_;