Add support for enabling DCHECKs in release mode

src/handles.cc

 // Copyright 2012 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/handles.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 80 matching lines @@
 
 DeferredHandleScope::DeferredHandleScope(Isolate* isolate)
     : impl_(isolate->handle_scope_implementer()) {
   impl_->BeginDeferredScope();
   HandleScopeData* data = impl_->isolate()->handle_scope_data();
   Object** new_next = impl_->GetSpareOrNewBlock();
   Object** new_limit = &new_next[kHandleBlockSize];
   DCHECK(data->limit == &impl_->blocks()->last()[kHandleBlockSize]);
   impl_->blocks()->Add(new_next);
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   prev_level_ = data->level;
 #endif
   data->level++;
   prev_limit_ = data->limit;
   prev_next_ = data->next;
   data->next = new_next;
   data->limit = new_limit;
 }
 
 
 DeferredHandleScope::~DeferredHandleScope() {
   impl_->isolate()->handle_scope_data()->level--;
   DCHECK(handles_detached_);
   DCHECK(impl_->isolate()->handle_scope_data()->level == prev_level_);
 }
 
 
 DeferredHandles* DeferredHandleScope::Detach() {
   DeferredHandles* deferred = impl_->Detach(prev_limit_);
   HandleScopeData* data = impl_->isolate()->handle_scope_data();
   data->next = prev_next_;
   data->limit = prev_limit_;
-#ifdef DEBUG
+#if DCHECK_IS_ON
   handles_detached_ = true;
 #endif
   return deferred;
 }
 
 } }  // namespace v8::internal