Simplify CheckPrototypeMaps.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 87592882e7b64d981e2ae41defda14e3945cb3cd..775e3a93965ca1522a0f3ce17c066653ad5835d5 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -3155,8 +3155,7 @@ void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
   Register reg = ToRegister(instr->temp());
 
   Handle<JSObject> holder = instr->holder();
-  Handle<Map> receiver_map = instr->receiver_map();
-  Handle<JSObject> current_prototype(JSObject::cast(receiver_map->prototype()));
+  Handle<JSObject> current_prototype = instr->prototype();
 
   // Load prototype object.
   LoadPrototype(reg, current_prototype);