[es6] conditionally ignore TDZ semantics for formals

src/preparser.cc

Index: src/preparser.cc
diff --git a/src/preparser.cc b/src/preparser.cc
index f7f8b2b8900412a1dad8279fbb5c368931dd30bb..29df7def66e8e0dbfc43fab8f855c4e00c6f87fd 100644
--- a/src/preparser.cc
+++ b/src/preparser.cc
@@ -103,7 +103,8 @@ PreParserExpression PreParserTraits::ParseFunctionLiteral(
 
 PreParser::PreParseResult PreParser::PreParseLazyFunction(
     LanguageMode language_mode, FunctionKind kind, bool has_simple_parameters,
-    ParserRecorder* log, Scanner::BookmarkScope* bookmark) {
+    bool has_parameter_expressions, ParserRecorder* log,
+    Scanner::BookmarkScope* bookmark) {
   log_ = log;
   // Lazy functions always have trivial outer scopes (no with/catch scopes).
   Scope* top_scope = NewScope(scope_, SCRIPT_SCOPE);
@@ -114,6 +115,7 @@ PreParser::PreParseResult PreParser::PreParseLazyFunction(
   Scope* function_scope = NewScope(
       scope_, IsArrowFunction(kind) ? ARROW_SCOPE : FUNCTION_SCOPE, kind);
   if (!has_simple_parameters) function_scope->SetHasNonSimpleParameters();
+  if (has_parameter_expressions) function_scope->SetHasParameterExpressions();
   PreParserFactory function_factory(NULL);
   FunctionState function_state(&function_state_, &scope_, function_scope, kind,
                                &function_factory);