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

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index 80f06c1a8cc9d70449377c857650b71b27707774..73ab4e3a87940681c8b4beb338e849500376f25c 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -6523,6 +6523,7 @@ void HOptimizedGraphBuilder::HandleGlobalVariableAssignment(
     HValue* name = Add<HConstant>(var->name());
     HValue* vector_value = Add<HConstant>(vector);
     HValue* slot_value = Add<HConstant>(vector->GetIndex(slot));
+    DCHECK_EQ(vector->GetLanguageMode(slot), function_language_mode());
     Callable callable = CodeFactory::StoreICInOptimizedCode(
         isolate(), function_language_mode());
     HValue* stub = Add<HConstant>(callable.code());
@@ -6856,6 +6857,7 @@ HInstruction* HOptimizedGraphBuilder::BuildNamedGeneric(
     return result;
 
   } else {
+    DCHECK_EQ(vector->GetLanguageMode(slot), function_language_mode());
     HValue* values[] = {object, key, value, slot_value, vector_value};
     if (vector->IsKeyedStoreIC(slot)) {
       // It's possible that a keyed store of a constant string was converted