[es6] More efficient way of marking AST call expressions in tail positions.

src/parsing/parser.h

Index: src/parsing/parser.h
diff --git a/src/parsing/parser.h b/src/parsing/parser.h
index 5f0176c76a7466f772292564056615cdc3e0baf9..87b6a910a458bb231687a0a4fb268d0194f99865 100644
--- a/src/parsing/parser.h
+++ b/src/parsing/parser.h
@@ -902,6 +902,8 @@ class Parser : public ParserBase<ParserTraits> {
   Statement* ParseForStatement(ZoneList<const AstRawString*>* labels, bool* ok);
   Statement* ParseThrowStatement(bool* ok);
   Expression* MakeCatchContext(Handle<String> id, VariableProxy* value);
+  class DontCollectExpressionsInTailPositionScope;
+  class CollectExpressionsInTailPositionToListScope;
   TryStatement* ParseTryStatement(bool* ok);
   DebuggerStatement* ParseDebuggerStatement(bool* ok);