Add support for enabling DCHECKs in release mode

src/heap/spaces.cc

 // Copyright 2011 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/bits.h"
 #include "src/base/platform/platform.h"
 #include "src/full-codegen.h"
 #include "src/heap/mark-compact.h"
@@ skipping 2521 matching lines @@
 
 
 void FreeList::RepairLists(Heap* heap) {
   small_list_.RepairFreeList(heap);
   medium_list_.RepairFreeList(heap);
   large_list_.RepairFreeList(heap);
   huge_list_.RepairFreeList(heap);
 }
 
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
 intptr_t FreeListCategory::SumFreeList() {
   intptr_t sum = 0;
   FreeListNode* cur = top();
   while (cur != NULL) {
     DCHECK(cur->map() == cur->GetHeap()->raw_unchecked_free_space_map());
     FreeSpace* cur_as_free_space = reinterpret_cast<FreeSpace*>(cur);
     sum += cur_as_free_space->nobarrier_size();
     cur = cur->next();
   }
   return sum;
@@ skipping 652 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }
 }  // namespace v8::internal