Add support for enabling DCHECKs in release mode

src/json-parser.h

 // 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.
 
 #ifndef V8_JSON_PARSER_H_
 #define V8_JSON_PARSER_H_
 
 #include "src/v8.h"
 
 #include "src/char-predicates-inl.h"
@@ skipping 330 matching lines @@
           Handle<Object> value = ParseJsonValue();
           if (value.is_null()) return ReportUnexpectedCharacter();
 
           JSObject::SetOwnElement(json_object, index, value, SLOPPY).Assert();
           continue;
         }
         // Not an index, fallback to the slow path.
       }
 
       position_ = start_position;
-#ifdef DEBUG
+#if DCHECK_IS_ON
       c0_ = '"';
 #endif
 
       Handle<String> key;
       Handle<Object> value;
 
       // Try to follow existing transitions as long as possible. Once we stop
       // transitioning, no transition can be found anymore.
       if (transitioning) {
         // First check whether there is a single expected transition. If so, try
@@ skipping 400 matching lines @@
       Object* element = string_table->KeyAt(entry);
       if (element == isolate()->heap()->undefined_value()) {
         // Lookup failure.
         result = factory()->InternalizeOneByteString(
             seq_source_, position_, length);
         break;
       }
       if (element != isolate()->heap()->the_hole_value() &&
           String::cast(element)->IsOneByteEqualTo(string_vector)) {
         result = Handle<String>(String::cast(element), isolate());
-#ifdef DEBUG
+#if DCHECK_IS_ON
         uint32_t hash_field =
             (hash << String::kHashShift) | String::kIsNotArrayIndexMask;
         DCHECK_EQ(static_cast<int>(result->Hash()),
                   static_cast<int>(hash_field >> String::kHashShift));
 #endif
         break;
       }
       entry = StringTable::NextProbe(entry, count++, capacity);
     }
     position_ = position;
@@ skipping 29 matching lines @@
 
   DCHECK_EQ('"', c0_);
   // Advance past the last '"'.
   AdvanceSkipWhitespace();
   return result;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_PARSER_H_