Properly complete in-object slack tracking.

src/objects.cc

 // 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.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 12501 matching lines @@
   int slack = *reinterpret_cast<int*>(data);
   map->SetInObjectProperties(map->GetInObjectProperties() - slack);
   map->set_unused_property_fields(map->unused_property_fields() - slack);
   map->set_instance_size(map->instance_size() - slack * kPointerSize);
   map->set_construction_counter(Map::kNoSlackTracking);
 
   // Visitor id might depend on the instance size, recalculate it.
   map->set_visitor_id(Heap::GetStaticVisitorIdForMap(map));
 }
 
+static void StopSlackTracking(Map* map, void* data) {
+  map->set_construction_counter(Map::kNoSlackTracking);
+}
 
 void Map::CompleteInobjectSlackTracking() {
   // Has to be an initial map.
   DCHECK(GetBackPointer()->IsUndefined());
 
   int slack = unused_property_fields();
   TransitionArray::TraverseTransitionTree(this, &GetMinInobjectSlack, &slack);
   if (slack != 0) {
     // Resize the initial map and all maps in its transition tree.
     TransitionArray::TraverseTransitionTree(this, &ShrinkInstanceSize, &slack);
+  } else {
+    TransitionArray::TraverseTransitionTree(this, &StopSlackTracking, nullptr);
   }
 }
 
 
 static bool PrototypeBenefitsFromNormalization(Handle<JSObject> object) {
   DisallowHeapAllocation no_gc;
   if (!object->HasFastProperties()) return false;
   Map* map = object->map();
   if (map->is_prototype_map()) return false;
   DescriptorArray* descriptors = map->instance_descriptors();
@@ skipping 7214 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8