Add a single-element global positive and negative cache to...

src/objects.cc

Index: src/objects.cc
===================================================================
--- src/objects.cc	(revision 4568)
+++ src/objects.cc	(working copy)
@@ -4900,6 +4900,7 @@
     // prototype is put into the initial map where it belongs.
     set_prototype_or_initial_map(value);
   }
+  Heap::ClearInstanceofCache();
   return value;
 }
 
@@ -5601,6 +5602,8 @@
   Map::cast(new_map)->set_prototype(value);
   real_receiver->set_map(Map::cast(new_map));
 
+  Heap::ClearInstanceofCache();
+
   return value;
 }