Add support for enabling DCHECKs in release mode

src/x64/deoptimizer-x64.cc

Index: src/x64/deoptimizer-x64.cc
diff --git a/src/x64/deoptimizer-x64.cc b/src/x64/deoptimizer-x64.cc
index 16b0cdcd1ba434abcdcc7d70302179cbbe97f616..64d3bd8c8ee357ed5a0301e96f81030476b5c4d6 100644
--- a/src/x64/deoptimizer-x64.cc
+++ b/src/x64/deoptimizer-x64.cc
@@ -55,7 +55,7 @@ void Deoptimizer::PatchCodeForDeoptimization(Isolate* isolate, Code* code) {
   // object was created, if necessary).
 
   Address instruction_start = code->instruction_start();
-#ifdef DEBUG
+#if DCHECK_IS_ON
   Address prev_call_address = NULL;
 #endif
   DeoptimizationInputData* deopt_data =
@@ -75,7 +75,7 @@ void Deoptimizer::PatchCodeForDeoptimization(Isolate* isolate, Code* code) {
     DCHECK(prev_call_address == NULL ||
            call_address >= prev_call_address + patch_size());
     DCHECK(call_address + patch_size() <= code->instruction_end());
-#ifdef DEBUG
+#if DCHECK_IS_ON
     prev_call_address = call_address;
 #endif
   }