Add support for enabling DCHECKs in release mode

src/hydrogen-environment-liveness.cc

 // Copyright 2013 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/hydrogen-environment-liveness.h"
 
 
 namespace v8 {
 namespace internal {
@@ skipping 201 matching lines @@
     ZapEnvironmentSlotsInSuccessors(block, &live);
   }
 
   // Finally, remove the HEnvironment{Bind,Lookup} markers.
   for (int i = 0; i < markers_.length(); ++i) {
     markers_[i]->DeleteAndReplaceWith(NULL);
   }
 }
 
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
 bool HEnvironmentLivenessAnalysisPhase::VerifyClosures(
     Handle<JSFunction> a, Handle<JSFunction> b) {
   Heap::RelocationLock for_heap_access(isolate()->heap());
   AllowHandleDereference for_verification;
   return a.is_identical_to(b);
 }
 #endif
 
 } }  // namespace v8::internal