[ic] Encode [Keyed]StoreIC's language mode in slot kind instead of code object's flags.

src/compiler/js-generic-lowering.cc

Index: src/compiler/js-generic-lowering.cc
diff --git a/src/compiler/js-generic-lowering.cc b/src/compiler/js-generic-lowering.cc
index d55c18038eb595f572e700ea5ccc2e72b1ea1629..c3af64d78894e142b7af44509f7eff19c98fa9cb 100644
--- a/src/compiler/js-generic-lowering.cc
+++ b/src/compiler/js-generic-lowering.cc
@@ -204,9 +204,8 @@ void JSGenericLowering::LowerJSStoreProperty(Node* node) {
   Node* value = NodeProperties::GetValueInput(node, 2);
   CallDescriptor::Flags flags = FrameStateFlagForCall(node);
   PropertyAccess const& p = PropertyAccessOf(node->op());
-  LanguageMode language_mode = p.language_mode();
   Callable callable =
-      CodeFactory::KeyedStoreICInOptimizedCode(isolate(), language_mode);
+      CodeFactory::KeyedStoreICInOptimizedCode(isolate(), p.language_mode());
   Node* vector = jsgraph()->HeapConstant(p.feedback().vector());
   typedef StoreWithVectorDescriptor Descriptor;
   node->InsertInputs(zone(), 0, 2);