Conditionally define PersistentNode destructor.

third_party/WebKit/Source/platform/heap/PersistentNode.h

Index: third_party/WebKit/Source/platform/heap/PersistentNode.h
diff --git a/third_party/WebKit/Source/platform/heap/PersistentNode.h b/third_party/WebKit/Source/platform/heap/PersistentNode.h
index 5fb806f8785784d323f997af1a5ba8c6a76a9b93..62d176d18f1ff5cc9fd0b762e6645167223de631 100644
--- a/third_party/WebKit/Source/platform/heap/PersistentNode.h
+++ b/third_party/WebKit/Source/platform/heap/PersistentNode.h
@@ -26,6 +26,7 @@ public:
         ASSERT(isUnused());
     }
 
+#if ENABLE(ASSERT)
     ~PersistentNode()
     {
         // If you hit this assert, it means that the thread finished
@@ -34,8 +35,9 @@ public:
         // main thread finishes without clearing all persistent handles.
         ASSERT(isMainThread() || isUnused());
     }
+#endif
 
-    // It is dangrous to copy the PersistentNode because it breaks the
+    // It is dangerous to copy the PersistentNode because it breaks the
     // free list.
     PersistentNode& operator=(const PersistentNode& otherref) = delete;