Keep prototype maps in dictionary mode until ICs see them

src/keys.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/keys.h"
 
 #include "src/api-arguments.h"
 #include "src/elements.h"
 #include "src/factory.h"
 #include "src/identity-map.h"
@@ skipping 139 matching lines @@
   // AdvanceFollowingProxies.
   if (mode_ == KeyCollectionMode::kOwnOnly && object->IsJSProxy()) {
     MAYBE_RETURN(CollectOwnJSProxyKeys(receiver, Handle<JSProxy>::cast(object)),
                  Nothing<bool>());
     return Just(true);
   }
 
   PrototypeIterator::WhereToEnd end = mode_ == KeyCollectionMode::kOwnOnly
                                           ? PrototypeIterator::END_AT_NON_HIDDEN
                                           : PrototypeIterator::END_AT_NULL;
-  for (PrototypeIterator iter(isolate_, object,
-                              PrototypeIterator::START_AT_RECEIVER, end);
+  for (PrototypeIterator iter(isolate_, object, kStartAtReceiver, end);
        !iter.IsAtEnd();) {
     Handle<JSReceiver> current =
         PrototypeIterator::GetCurrent<JSReceiver>(iter);
     Maybe<bool> result = Just(false);  // Dummy initialization.
     if (current->IsJSProxy()) {
       result = CollectOwnJSProxyKeys(receiver, Handle<JSProxy>::cast(current));
     } else {
       DCHECK(current->IsJSObject());
       result = CollectOwnKeys(receiver, Handle<JSObject>::cast(current));
     }
@@ skipping 570 matching lines @@
       isolate_, keys, JSReceiver::OwnPropertyKeys(target), Nothing<bool>());
   bool prev_filter_proxy_keys_ = filter_proxy_keys_;
   filter_proxy_keys_ = false;
   Maybe<bool> result = AddKeysFromJSProxy(proxy, keys);
   filter_proxy_keys_ = prev_filter_proxy_keys_;
   return result;
 }
 
 }  // namespace internal
 }  // namespace v8