Use a dictionary-mode code cache on the map rather than a dual system.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index a4d1ada86adf84432cb7ef8d662f810a3c43707d..0efc8f6384816d67e7a3cd1ae6e2468bfa7dafa5 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -7353,7 +7353,7 @@ class Internals {
   static const int kNodeIsPartiallyDependentShift = 4;
   static const int kNodeIsActiveShift = 4;
 
-  static const int kJSObjectType = 0xb8;
+  static const int kJSObjectType = 0xb6;
   static const int kFirstNonstringType = 0x80;
   static const int kOddballType = 0x83;
   static const int kForeignType = 0x87;