Use atomic operation to read the length of a fixed array.

src/layout-descriptor.cc

 // Copyright 2014 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 <sstream>
 
 #include "src/v8.h"
 
 #include "src/base/bits.h"
 #include "src/layout-descriptor.h"
@@ skipping 227 matching lines @@
   // It must not become fast-mode descriptor here, because otherwise it has to
   // be fast pointer layout descriptor already but it's is slow mode now.
   DCHECK_LT(kSmiValueSize, layout_descriptor_length);
 
   // Trim, clean and reinitialize this slow-mode layout descriptor.
   int array_length = GetSlowModeBackingStoreLength(layout_descriptor_length);
   int current_length = length();
   if (current_length != array_length) {
     DCHECK_LT(array_length, current_length);
     int delta = current_length - array_length;
-    heap->RightTrimFixedArray<Heap::FROM_GC>(this, delta);
+    heap->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(this, delta);
   }
   memset(DataPtr(), 0, DataSize());
   LayoutDescriptor* layout_descriptor =
       Initialize(this, map, descriptors, num_descriptors);
   DCHECK_EQ(this, layout_descriptor);
   return layout_descriptor;
 }
 
 
 bool LayoutDescriptor::IsConsistentWithMap(Map* map, bool check_tail) {
@@ skipping 20 matching lines @@
       int n = capacity();
       for (int i = last_field_index; i < n; i++) {
         DCHECK(IsTagged(i));
       }
     }
   }
   return true;
 }
 }
 }  // namespace v8::internal