[api] Add a switch that controls if ES2015 tail call elimination feature is enabled or not.

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index e3063d8b1fc251ddc5b493391e5fbb858ad097ad..22f74807fbadfd382d89c298158638c4bbedcdbd 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -784,7 +784,8 @@ Parser::Parser(ParseInfo* info)
   DCHECK(!info->script().is_null() || info->source_stream() != NULL);
   set_allow_lazy(info->allow_lazy_parsing());
   set_allow_natives(FLAG_allow_natives_syntax || info->is_native());
-  set_allow_tailcalls(FLAG_harmony_tailcalls && !info->is_native());
+  set_allow_tailcalls(FLAG_harmony_tailcalls && !info->is_native() &&
+                      info->isolate()->is_tail_call_elimination_enabled());
   set_allow_harmony_sloppy(FLAG_harmony_sloppy);
   set_allow_harmony_sloppy_function(FLAG_harmony_sloppy_function);
   set_allow_harmony_sloppy_let(FLAG_harmony_sloppy_let);