Add support for enabling DCHECKs in release mode

src/optimizing-compiler-thread.h

Index: src/optimizing-compiler-thread.h
diff --git a/src/optimizing-compiler-thread.h b/src/optimizing-compiler-thread.h
index 60f95f4ea44ee4c89cc84f89a53ecdb5d9a3b2ee..f9ed3bdf314ba6d7adc53fc222fae80a65c8f50f 100644
--- a/src/optimizing-compiler-thread.h
+++ b/src/optimizing-compiler-thread.h
@@ -24,7 +24,7 @@ class OptimizingCompilerThread : public base::Thread {
  public:
   explicit OptimizingCompilerThread(Isolate* isolate)
       : Thread(Options("OptimizingCompilerThread")),
-#ifdef DEBUG
+#if DCHECK_IS_ON
         thread_id_(0),
 #endif
         isolate_(isolate),
@@ -80,7 +80,7 @@ class OptimizingCompilerThread : public base::Thread {
     return (FLAG_concurrent_recompilation && max_available > 1);
   }
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   static bool IsOptimizerThread(Isolate* isolate);
   bool IsOptimizerThread();
 #endif
@@ -107,7 +107,7 @@ class OptimizingCompilerThread : public base::Thread {
     return result;
   }
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   int thread_id_;
   base::Mutex thread_id_mutex_;
 #endif