Removed unused field, making clang happy again.

R=marja@chromium.org

Review URL: https://codereview.chromium.org/163233003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19353 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/preparser.h

@@ -692,7 +692,6 @@ class PreParser : public ParserBase<PreParserTraits> {
 
     int materialized_literal_count_;
     int expected_properties_;
-    LanguageMode language_mode_;
     bool is_generator_;
   };