Add support for enabling DCHECKs in release mode

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index ebd9e8b015d165c63cb21fcc8e69c530b93e3078..f9470c42fc88ca6c386a167a7057f5af26ef7569 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -159,7 +159,7 @@ class HBasicBlock FINAL : public ZoneObject {
 
   inline Zone* zone() const;
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   void Verify();
 #endif
 
@@ -375,7 +375,7 @@ class HGraph FINAL : public ZoneObject {
 
   bool Optimize(BailoutReason* bailout_reason);
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   void Verify(bool do_full_verify) const;
 #endif
 
@@ -800,7 +800,7 @@ class AstContext {
 
   // We want to be able to assert, in a context-specific way, that the stack
   // height makes sense when the context is filled.
-#ifdef DEBUG
+#if DCHECK_IS_ON
   int original_length_;
 #endif
 
@@ -2253,7 +2253,7 @@ class HOptimizedGraphBuilder : public HGraphBuilder, public AstVisitor {
       HEnvironmentMarker* bind =
           Add<HEnvironmentMarker>(HEnvironmentMarker::BIND, index);
       USE(bind);
-#ifdef DEBUG
+#if DCHECK_IS_ON
       bind->set_closure(env->closure());
 #endif
     }
@@ -2266,7 +2266,7 @@ class HOptimizedGraphBuilder : public HGraphBuilder, public AstVisitor {
       HEnvironmentMarker* lookup =
           Add<HEnvironmentMarker>(HEnvironmentMarker::LOOKUP, index);
       USE(lookup);
-#ifdef DEBUG
+#if DCHECK_IS_ON
       lookup->set_closure(env->closure());
 #endif
     }