Add support for enabling DCHECKs in release mode

src/assert-scope.h

Index: src/assert-scope.h
diff --git a/src/assert-scope.h b/src/assert-scope.h
index 0f1e056fbac711ecc82e937a858e021f1a91574c..e81a3647d7029ff5779e11a36725c386766c6241 100644
--- a/src/assert-scope.h
+++ b/src/assert-scope.h
@@ -70,9 +70,8 @@ class PerIsolateAssertScope {
 
 
 template <PerThreadAssertType type, bool allow>
-#ifdef DEBUG
-class PerThreadAssertScopeDebugOnly : public
-    PerThreadAssertScope<type, allow> {
+#if DCHECK_IS_ON
+class PerThreadAssertScopeDebugOnly : public PerThreadAssertScope<type, allow> {
 #else
 class PerThreadAssertScopeDebugOnly {
  public:
@@ -82,9 +81,9 @@ class PerThreadAssertScopeDebugOnly {
 
 
 template <PerIsolateAssertType type, bool allow>
-#ifdef DEBUG
-class PerIsolateAssertScopeDebugOnly : public
-    PerIsolateAssertScope<type, allow> {
+#if DCHECK_IS_ON
+class PerIsolateAssertScopeDebugOnly
+    : public PerIsolateAssertScope<type, allow> {
  public:
   explicit PerIsolateAssertScopeDebugOnly(Isolate* isolate)
       : PerIsolateAssertScope<type, allow>(isolate) { }