Add support for enabling DCHECKs in release mode

src/bignum.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/bignum.h"
 #include "src/utils.h"
 
 namespace v8 {
@@ skipping 696 matching lines @@
     carry = new_carry;
   }
   if (carry != 0) {
     bigits_[used_digits_] = carry;
     used_digits_++;
   }
 }
 
 
 void Bignum::SubtractTimes(const Bignum& other, int factor) {
-#ifdef DEBUG
+#if DCHECK_IS_ON
   Bignum a, b;
   a.AssignBignum(*this);
   b.AssignBignum(other);
   b.MultiplyByUInt32(factor);
   a.SubtractBignum(b);
 #endif
   DCHECK(exponent_ <= other.exponent_);
   if (factor < 3) {
     for (int i = 0; i < factor; ++i) {
       SubtractBignum(other);
@@ skipping 16 matching lines @@
     Chunk difference = bigits_[i] - borrow;
     bigits_[i] = difference & kBigitMask;
     borrow = difference >> (kChunkSize - 1);
   }
   Clamp();
   DCHECK(Bignum::Equal(a, *this));
 }
 
 
 } }  // namespace v8::internal