Experimental parser: crash fix.

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 3cbd0dd9e557d5bb1c670bd0444863abcd1853dd..ad57384549551aef0075df7a6fb66a3358de789d 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -49,10 +49,7 @@ class ParserBase {
         allow_for_of_(false) { }
   // TODO(mstarzinger): Only virtual until message reporting has been unified.
   // FIXME: Might need to continue to be virtual for the experimental branch.
-  virtual ~ParserBase() {
-    delete scanner_;
-    scanner_ = NULL;
-  }
+  virtual ~ParserBase() { }
 
   // Getters that indicate whether certain syntactical constructs are
   // allowed to be parsed by this instance of the parser.