Define DEBUG for v8_optimized_debug=2

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 4a08319044bf7f0768970f539a1a41ac3f298747..062019af4604f0288e1ad2802baba825d75c28ef 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -419,8 +419,8 @@ class Vector {
   // Returns a vector using the same backing storage as this one,
   // spanning from and including 'from', to but not including 'to'.
   Vector<T> SubVector(int from, int to) {
-    ASSERT(to <= length_);
-    ASSERT(from < to);
+    SLOW_ASSERT(to <= length_);
+    SLOW_ASSERT(from < to);
     ASSERT(0 <= from);
     return Vector<T>(start() + from, to - from);
   }