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

src/ic/x64/handler-compiler-x64.cc

Index: src/ic/x64/handler-compiler-x64.cc
diff --git a/src/ic/x64/handler-compiler-x64.cc b/src/ic/x64/handler-compiler-x64.cc
index c2f5381f892b99a2f43015e9e8a2ee102de80d6a..63d4cddf217557c105c0cb5b13ac38c65305e585 100644
--- a/src/ic/x64/handler-compiler-x64.cc
+++ b/src/ic/x64/handler-compiler-x64.cc
@@ -756,7 +756,7 @@ Handle<Code> NamedStoreHandlerCompiler::CompileStoreCallback(
   __ TailCallRuntime(Runtime::kStoreCallbackProperty);
 
   // Return the generated code.
-  return GetCode(kind(), Code::FAST, name);
+  return GetCode(kind(), name);
 }
 
 
@@ -798,7 +798,7 @@ Handle<Code> NamedLoadHandlerCompiler::CompileLoadGlobal(
   FrontendFooter(name, &miss);
 
   // Return the generated code.
-  return GetCode(kind(), Code::NORMAL, name);
+  return GetCode(kind(), name);
 }