Use no barrier size accessor in FreeListCategory::SumFreeList.

src/spaces.cc

Index: src/spaces.cc
diff --git a/src/spaces.cc b/src/spaces.cc
index 20efbf72e080f36d8fe9e50833cce25043f7c928..59c17af1a682f895da807efe188584cb698e9507 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -2491,7 +2491,7 @@ intptr_t FreeListCategory::SumFreeList() {
   while (cur != NULL) {
     ASSERT(cur->map() == cur->GetHeap()->raw_unchecked_free_space_map());
     FreeSpace* cur_as_free_space = reinterpret_cast<FreeSpace*>(cur);
-    sum += cur_as_free_space->Size();
+    sum += cur_as_free_space->nobarrier_size();
     cur = cur->next();
   }
   return sum;