[es6] conditionally ignore TDZ semantics for formals

src/expression-classifier.h

Index: src/expression-classifier.h
diff --git a/src/expression-classifier.h b/src/expression-classifier.h
index fb45f41fa169368b998aacf33afdeaf33e44ec51..a20d29f011d85c4c59a7be7010a25095e5f71a2c 100644
--- a/src/expression-classifier.h
+++ b/src/expression-classifier.h
@@ -48,7 +48,11 @@ class ExpressionClassifier {
                       ArrowFormalParametersProduction)
   };
 
-  enum FunctionProperties { NonSimpleParameter = 1 << 0 };
+  enum FunctionProperties {
+    NonSimpleParameter = 1 << 0,
+    ContainsExpressions = 1 << 1,
+    ArgumentsParameter = 1 << 2
+  };
 
   ExpressionClassifier()
       : invalid_productions_(0),
@@ -136,6 +140,22 @@ class ExpressionClassifier {
     function_properties_ |= NonSimpleParameter;
   }
 
+  bool contains_expressions() const {
+    return (function_properties_ & ContainsExpressions);
+  }
+
+  void RecordContainsExpressions() {
+    function_properties_ |= ContainsExpressions;
+  }
+
+  bool has_arguments_parameter() const {
+    return (function_properties_ & ArgumentsParameter);
+  }
+
+  void RecordArgumentsParameter() {
+    function_properties_ |= ArgumentsParameter;
+  }
+
   void RecordExpressionError(const Scanner::Location& loc,
                              MessageTemplate::Template message,
                              const char* arg = nullptr) {