Fix bug introduced when extracting utils.

src/v8utils.h

Index: src/v8utils.h
diff --git a/src/v8utils.h b/src/v8utils.h
index 3f272dd32e0ffa304ef761ceea6e260df30bf656..a907c9f55632d2a7cfc04d77e94c005bdf8d1b14 100644
--- a/src/v8utils.h
+++ b/src/v8utils.h
@@ -184,7 +184,7 @@ class StringBuilder {
   StringBuilder(char* buffer, int size)
       : buffer_(buffer, size), position_(0) { }
 
-  ~StringBuilder() { if (!is_finalized()) buffer_.Dispose(); }
+  ~StringBuilder() { if (!is_finalized()) Finalize(); }
 
   int size() const { return buffer_.length(); }