Layout descriptor must be trimmed when corresponding descriptors array is trimmed to stay in sync.

src/heap/mark-compact.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 2591 matching lines @@
   int number_of_descriptors = descriptors->number_of_descriptors_storage();
   int to_trim = number_of_descriptors - number_of_own_descriptors;
   if (to_trim == 0) return;
 
   heap_->RightTrimFixedArray<Heap::FROM_GC>(
       descriptors, to_trim * DescriptorArray::kDescriptorSize);
   descriptors->SetNumberOfDescriptors(number_of_own_descriptors);
 
   if (descriptors->HasEnumCache()) TrimEnumCache(map, descriptors);
   descriptors->Sort();
+
+  if (FLAG_unbox_double_fields) {
+    LayoutDescriptor* layout_descriptor = map->layout_descriptor();
+    layout_descriptor = layout_descriptor->Trim(heap_, map, descriptors,
+                                                number_of_own_descriptors);
+    SLOW_DCHECK(layout_descriptor->IsConsistentWithMap(map, true));
+  }
 }
 
 
 void MarkCompactCollector::TrimEnumCache(Map* map,
                                          DescriptorArray* descriptors) {
   int live_enum = map->EnumLength();
   if (live_enum == kInvalidEnumCacheSentinel) {
     live_enum = map->NumberOfDescribedProperties(OWN_DESCRIPTORS, DONT_ENUM);
   }
   if (live_enum == 0) return descriptors->ClearEnumCache();
@@ skipping 2139 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }
 }  // namespace v8::internal