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 dde61691d5888861f6f1c29fe372fde305a064cb..ffefeee43c3f0756c0a50187e67e12d6b04b43ff 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);
 }