Revert of Internalize strings in-place

src/runtime/runtime-object.cc

Index: src/runtime/runtime-object.cc
diff --git a/src/runtime/runtime-object.cc b/src/runtime/runtime-object.cc
index 397ad6c383d2ae9b55418bc5f6e9a126528b0e47..9d7a4569e707df0f5f8801e0df364676749b5730 100644
--- a/src/runtime/runtime-object.cc
+++ b/src/runtime/runtime-object.cc
@@ -56,14 +56,6 @@ static MaybeHandle<Object> KeyedGetObjectProperty(Isolate* isolate,
       DisallowHeapAllocation no_allocation;
       Handle<JSObject> receiver = Handle<JSObject>::cast(receiver_obj);
       Handle<Name> key = Handle<Name>::cast(key_obj);
-      // Get to a ThinString's referenced internalized string, but don't
-      // otherwise force internalization. We assume that internalization
-      // (which is a dictionary lookup with a non-internalized key) is
-      // about as expensive as doing the property dictionary lookup with
-      // the non-internalized key directly.
-      if (key->IsThinString()) {
-        key = handle(Handle<ThinString>::cast(key)->actual(), isolate);
-      }
       if (receiver->IsJSGlobalObject()) {
         // Attempt dictionary lookup.
         GlobalDictionary* dictionary = receiver->global_dictionary();