[cleanup] Return object instead of map.

No need to return an empty map. Return a JSObject instead.

Bug: v8:5933
Change-Id: I9fb727c5e1920ba94fd3d5e7ef2a7d9d602f56d8
Reviewed-on: https://chromium-review.googlesource.com/506194Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Franziska Hinkelmann <franzih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45350}

src/feedback-vector.cc

@@ -1014,7 +1014,7 @@ JSObject* CollectTypeProfileNexus::GetTypeProfile() const {
   Object* const feedback = GetFeedback();
 
   if (feedback == *FeedbackVector::UninitializedSentinel(isolate)) {
-    return *isolate->factory()->NewJSMap();
+    return *isolate->factory()->NewJSObject(isolate->object_function());
   }
 
   return *ConvertToJSObject(