Add support for enabling DCHECKs in release mode

src/handles-inl.h

 // Copyright 2006-2008 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.
 //
 
 #ifndef V8_HANDLES_INL_H_
 #define V8_HANDLES_INL_H_
 
 #include "src/api.h"
 #include "src/handles.h"
@@ skipping 33 matching lines @@
   return *bit_cast<T**>(location_);
 }
 
 template <typename T>
 inline T** Handle<T>::location() const {
   SLOW_DCHECK(location_ == NULL ||
               IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));
   return location_;
 }
 
-#ifdef DEBUG
+#ifdef ENABLE_SLOW_DCHECKS
 template <typename T>
 bool Handle<T>::IsDereferenceAllowed(DereferenceCheckMode mode) const {
   DCHECK(location_ != NULL);
   Object* object = *bit_cast<T**>(location_);
   if (object->IsSmi()) return true;
   HeapObject* heap_object = HeapObject::cast(object);
   Heap* heap = heap_object->GetHeap();
   Object** handle = reinterpret_cast<Object**>(location_);
   Object** roots_array_start = heap->roots_array_start();
   if (roots_array_start <= handle &&
@@ skipping 80 matching lines @@
   // handle, and return the result.
   DCHECK(cur < current->limit);
   current->next = cur + 1;
 
   T** result = reinterpret_cast<T**>(cur);
   *result = value;
   return result;
 }
 
 
 #ifdef DEBUG

[Jakob Kummerow, 2014/12/03 10:53:53]

Forgot this one? Declaration in handles.h would need updating too.

 inline SealHandleScope::SealHandleScope(Isolate* isolate) : isolate_(isolate) {
   // Make sure the current thread is allowed to create handles to begin with.
   CHECK(AllowHandleAllocation::IsAllowed());
   HandleScopeData* current = isolate_->handle_scope_data();
   // Shrink the current handle scope to make it impossible to do
   // handle allocations without an explicit handle scope.
   limit_ = current->limit;
   current->limit = current->next;
   level_ = current->level;
   current->level = 0;
 }
 
 
 inline SealHandleScope::~SealHandleScope() {
   // Restore state in current handle scope to re-enable handle
   // allocations.
   HandleScopeData* current = isolate_->handle_scope_data();
   DCHECK_EQ(0, current->level);
   current->level = level_;
   DCHECK_EQ(current->next, current->limit);
   current->limit = limit_;
 }
 
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_INL_H_