Reland of [stubs] Port KeyedLoadIC_Generic stub to TurboFan

src/code-factory.cc

Index: src/code-factory.cc
diff --git a/src/code-factory.cc b/src/code-factory.cc
index 654c192fc773db9d346118541ddd526139de0d6b..06bccf23faada7b8aabca37276fcb4bfc9c18900 100644
--- a/src/code-factory.cc
+++ b/src/code-factory.cc
@@ -82,6 +82,10 @@ Callable CodeFactory::KeyedLoadICInOptimizedCode(Isolate* isolate) {
 
 // static
 Callable CodeFactory::KeyedLoadIC_Megamorphic(Isolate* isolate) {
+  if (FLAG_tf_load_ic_stub) {
+    return Callable(isolate->builtins()->KeyedLoadIC_Megamorphic_TF(),
+                    LoadWithVectorDescriptor(isolate));
+  }
   return Callable(isolate->builtins()->KeyedLoadIC_Megamorphic(),
                   LoadWithVectorDescriptor(isolate));
 }