Move some code from Runtime_GetPrototype into a new Object::GetPrototype.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 3bda179712b010834977212ceffa36772927a94a..11b40674b241ccd69b2a47bb6da8cf0f70db3d0e 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1199,15 +1199,22 @@ MaybeHandle<Object> Object::SetElement(Isolate* isolate, Handle<Object> object,
 }
 
 
-Handle<Object> Object::GetPrototypeSkipHiddenPrototypes(
-    Isolate* isolate, Handle<Object> receiver) {
-  PrototypeIterator iter(isolate, receiver);
-  while (!iter.IsAtEnd(PrototypeIterator::END_AT_NON_HIDDEN)) {
+Handle<Object> Object::GetPrototype(Isolate* isolate, Handle<Object> obj) {
+  // We don't expect access checks to be needed on JSProxy objects.
+  DCHECK(!obj->IsAccessCheckNeeded() || obj->IsJSObject());
+  Handle<Context> context(isolate->context());
+  if (obj->IsAccessCheckNeeded() &&
+      !isolate->MayAccess(context, Handle<JSObject>::cast(obj))) {
+    return isolate->factory()->null_value();
+  }
+
+  PrototypeIterator iter(isolate, obj, PrototypeIterator::START_AT_RECEIVER);
+  do {
+    iter.AdvanceIgnoringProxies();
     if (PrototypeIterator::GetCurrent(iter)->IsJSProxy()) {
       return PrototypeIterator::GetCurrent(iter);
     }
-    iter.Advance();
-  }
+  } while (!iter.IsAtEnd(PrototypeIterator::END_AT_NON_HIDDEN));
   return PrototypeIterator::GetCurrent(iter);
 }