[es8] Prepare explicit tail calls (STC) for staging with implicit tail calls (PTC).

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index ce3dd20d359310a1b89eda3d05c88551127537d8..8618b2d8003a0074e368e2ab137e5a1b94fa0aa5 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -2657,8 +2657,7 @@ Statement* Parser::ParseReturnStatement(bool* ok) {
 
       if (allow_tailcalls() && !is_sloppy(language_mode())) {
         // ES6 14.6.1 Static Semantics: IsInTailPosition
-        Scanner::Location loc(pos, pos + 1);
-        function_state_->AddExpressionInTailPosition(return_value, loc);
+        function_state_->AddProperTailCallExpression(return_value);
       }
     }
   }
@@ -2989,7 +2988,7 @@ TryStatement* Parser::ParseTryStatement(bool* ok) {
                                              catch_variable, catch_block, pos);
   } else {
     if (FLAG_harmony_explicit_tailcalls &&
-        !tail_call_expressions_in_catch_block.is_empty()) {
+        tail_call_expressions_in_catch_block.has_syntactic_tail_calls()) {
       // TODO(ishell): update chapter number.
       // ES8 XX.YY.ZZ
       ReportMessageAt(tail_call_expressions_in_catch_block.location(),