[turbofan] Reduce JSLoadProperty and JSStoreProperty of strings to JSLoadNamed and JSStoreNamed.

src/compiler/js-type-feedback.h

Index: src/compiler/js-type-feedback.h
diff --git a/src/compiler/js-type-feedback.h b/src/compiler/js-type-feedback.h
index 033da657ff7ca9b29b5c373578ec0ced3bbe8120..91c3d2e5e831906ce6fa6cb5d721e46337162b2e 100644
--- a/src/compiler/js-type-feedback.h
+++ b/src/compiler/js-type-feedback.h
@@ -74,6 +74,7 @@ class JSTypeFeedbackSpecializer : public Reducer {
 
   TypeFeedbackOracle* oracle() { return oracle_; }
   Graph* graph() { return jsgraph_->graph(); }
+  JSGraph* jsgraph() { return jsgraph_; }
   CommonOperatorBuilder* common() { return jsgraph_->common(); }
   SimplifiedOperatorBuilder* simplified() { return &simplified_; }