[proxies] use [[GetPrototypeOf]] trap in for-in

src/objects.h

 // Copyright 2015 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/assert-scope.h"
@@ skipping 1944 matching lines @@
   // ES6 [[OwnPropertyKeys]] (modulo return type)
   MUST_USE_RESULT static MaybeHandle<FixedArray> OwnPropertyKeys(
       Handle<JSReceiver> object) {
     return GetKeys(object, OWN_ONLY, ALL_PROPERTIES, CONVERT_TO_STRING);
   }
 
   // Computes the enumerable keys for a JSObject. Used for implementing
   // "for (n in object) { }".
   MUST_USE_RESULT static MaybeHandle<FixedArray> GetKeys(
       Handle<JSReceiver> object, KeyCollectionType type, PropertyFilter filter,
-      GetKeysConversion keys_conversion = KEEP_NUMBERS);
+      GetKeysConversion keys_conversion = KEEP_NUMBERS,
+      bool filter_proxy_keys_ = true);
 
   MUST_USE_RESULT static MaybeHandle<FixedArray> GetOwnValues(
       Handle<JSReceiver> object, PropertyFilter filter);
 
   MUST_USE_RESULT static MaybeHandle<FixedArray> GetOwnEntries(
       Handle<JSReceiver> object, PropertyFilter filter);
 
   // Layout description.
   static const int kPropertiesOffset = HeapObject::kHeaderSize;
   static const int kHeaderSize = HeapObject::kHeaderSize + kPointerSize;
@@ skipping 8920 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_