Ensure slow properties for simple {__proto__:null} literals.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index c9eee390e99c4aa8e76501f26783dab1aa1e267e..e2529aee43d43f5354fa09e339fd3bb981c219e3 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2796,6 +2796,10 @@ class FixedArray: public FixedArrayBase {
   static const int kMaxSize = 128 * MB * kPointerSize;
   // Maximally allowed length of a FixedArray.
   static const int kMaxLength = (kMaxSize - kHeaderSize) / kPointerSize;
+  // Maximally allowed length for regular (non large object space) object.
+  STATIC_ASSERT(kMaxRegularHeapObjectSize < kMaxSize);
+  static const int kMaxRegularLength =
+      (kMaxRegularHeapObjectSize - kHeaderSize) / kPointerSize;
 
   // Dispatched behavior.
   DECLARE_PRINTER(FixedArray)
@@ -6004,6 +6008,9 @@ class Map: public HeapObject {
   static Handle<Map> CopyInitialMap(Handle<Map> map, int instance_size,
                                     int in_object_properties,
                                     int unused_property_fields);
+  static Handle<Map> CopyInitialMapNormalized(
+      Handle<Map> map,
+      PropertyNormalizationMode mode = CLEAR_INOBJECT_PROPERTIES);
   static Handle<Map> CopyDropDescriptors(Handle<Map> map);
   static Handle<Map> CopyInsertDescriptor(Handle<Map> map,
                                           Descriptor* descriptor,