Use POLYMORPHIC for polymorphic Keyed(Load|Store)IC

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 994b5bcd0ad6c0aa617b7498a5c34ba5bb1ef17a..82727ef14ece23c6cbf1ddb50e6cdc679a89c3a0 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -2772,7 +2772,7 @@ Handle<Code> KeyedStoreStubCompiler::CompileStorePolymorphic(
   __ jmp(ic, RelocInfo::CODE_TARGET);
 
   // Return the generated code.
-  return GetCode(Code::NORMAL, factory()->empty_string(), MEGAMORPHIC);
+  return GetCode(Code::NORMAL, factory()->empty_string(), POLYMORPHIC);
 }
 
 
@@ -3253,7 +3253,7 @@ Handle<Code> KeyedLoadStubCompiler::CompileLoadPolymorphic(
   GenerateLoadMiss(masm(), Code::KEYED_LOAD_IC);
 
   // Return the generated code.
-  return GetCode(Code::NORMAL, factory()->empty_string(), MEGAMORPHIC);
+  return GetCode(Code::NORMAL, factory()->empty_string(), POLYMORPHIC);
 }