Experimental scanner: fix harmony flag setting.

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 4dfa19c7d2b2bd061b5fa9eb8a818e2ce367baa2..3cbd0dd9e557d5bb1c670bd0444863abcd1853dd 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -48,7 +48,11 @@ class ParserBase {
         allow_generators_(false),
         allow_for_of_(false) { }
   // TODO(mstarzinger): Only virtual until message reporting has been unified.
-  virtual ~ParserBase() { }
+  // FIXME: Might need to continue to be virtual for the experimental branch.
+  virtual ~ParserBase() {
+    delete scanner_;
+    scanner_ = NULL;
+  }
 
   // Getters that indicate whether certain syntactical constructs are
   // allowed to be parsed by this instance of the parser.