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

test/cctest/test-heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5310 matching lines @@
                                          int initial_length,
                                          int elements_to_trim) {
   v8::HandleScope scope(CcTest::isolate());
   Isolate* isolate = CcTest::i_isolate();
   Factory* factory = isolate->factory();
   Heap* heap = isolate->heap();
 
   Handle<FixedTypedArrayBase> array =
       factory->NewFixedTypedArray(initial_length, type);
   int old_size = array->size();
-  heap->RightTrimFixedArray<Heap::FROM_MUTATOR>(*array, elements_to_trim);
+  heap->RightTrimFixedArray<Heap::CONCURRENT_TO_SWEEPER>(*array,
+                                                         elements_to_trim);
 
   // Check that free space filler is at the right place and did not smash the
   // array header.
   CHECK(array->IsFixedArrayBase());
   CHECK_EQ(initial_length - elements_to_trim, array->length());
   int new_size = array->size();
   if (new_size != old_size) {
     // Free space filler should be created in this case.
     Address next_obj_address = array->address() + array->size();
     CHECK(HeapObject::FromAddress(next_obj_address)->IsFiller());
@@ skipping 17 matching lines @@
   TestRightTrimFixedTypedArray(v8::kExternalUint32Array, 8, 6);
   TestRightTrimFixedTypedArray(v8::kExternalUint32Array, 8 - 1, 6);
 
   // 32-bit cases.
   TestRightTrimFixedTypedArray(v8::kExternalUint8Array, 16, 3);
   TestRightTrimFixedTypedArray(v8::kExternalUint8Array, 16 - 3, 3);
   TestRightTrimFixedTypedArray(v8::kExternalUint16Array, 8, 3);
   TestRightTrimFixedTypedArray(v8::kExternalUint16Array, 8 - 1, 3);
   TestRightTrimFixedTypedArray(v8::kExternalUint32Array, 4, 3);
 }