Probe keyed load cache in generic keyed load stub....

src/assembler.h

Index: src/assembler.h
===================================================================
--- src/assembler.h	(revision 3428)
+++ src/assembler.h	(working copy)
@@ -401,6 +401,10 @@
   static ExternalReference builtin_passed_function();
   static ExternalReference random_positive_smi_function();
 
+  // Static data in the keyed lookup cache.
+  static ExternalReference keyed_lookup_cache_keys();
+  static ExternalReference keyed_lookup_cache_field_offsets();
+
   // Static variable Factory::the_hole_value.location()
   static ExternalReference the_hole_value_location();