Only use the non-strict-arguments-stub if the store site is non-strict.

src/ic.cc

Index: src/ic.cc
diff --git a/src/ic.cc b/src/ic.cc
index 2607bb3b68d53405be03865fe60538dea4e8b9e0..3c9f1b66922f147ee4f28925dfdef34ce96f1dc2 100644
--- a/src/ic.cc
+++ b/src/ic.cc
@@ -1689,7 +1689,9 @@ MaybeObject* KeyedStoreIC::Store(Handle<Object> object,
         bool key_is_smi_like = key->IsSmi() || !key->ToSmi()->IsFailure();
         if (receiver->elements()->map() ==
             isolate()->heap()->non_strict_arguments_elements_map()) {
-          stub = non_strict_arguments_stub();
+          if (strict_mode() == kNonStrictMode) {
+            stub = non_strict_arguments_stub();
+          }
         } else if (key_is_smi_like &&
                    !(target().is_identical_to(non_strict_arguments_stub()))) {
           // We should go generic if receiver isn't a dictionary, but our