Partially revert r29468

src/objects-inl.h

 // Copyright 2012 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 6928 matching lines @@
 void Map::ClearCodeCache(Heap* heap) {
   // No write barrier is needed since empty_fixed_array is not in new space.
   // Please note this function is used during marking:
   //  - MarkCompactCollector::MarkUnmarkedObject
   //  - IncrementalMarking::Step
   DCHECK(!heap->InNewSpace(heap->empty_fixed_array()));
   WRITE_FIELD(this, kCodeCacheOffset, heap->empty_fixed_array());
 }
 
 
-int Map::SlackForArraySize(bool is_prototype_map, int old_size,
-                           int size_limit) {
+int Map::SlackForArraySize(int old_size, int size_limit) {
   const int max_slack = size_limit - old_size;
   CHECK_LE(0, max_slack);
-  if (old_size < 4) return Min(max_slack, 1);
-  if (is_prototype_map) return Min(max_slack, 4);
+  if (old_size < 4) {
+    DCHECK_LE(1, max_slack);
+    return 1;
+  }
   return Min(max_slack, old_size / 4);
 }
 
 
 void JSArray::set_length(Smi* length) {
   // Don't need a write barrier for a Smi.
   set_length(static_cast<Object*>(length), SKIP_WRITE_BARRIER);
 }
 
 
@@ skipping 349 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_