[parser] Lift template literal invalid escape restriction

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 915b2e6a694107351fc160cb8d88cd3eb5e9eaaa..3e5aa3cb445aa285ed72631a0805ca58f42cec1a 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -3535,6 +3535,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_trailing_commas)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_class_fields)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_object_rest_spread)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_dynamic_import)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_template_escapes)
 
 void InstallPublicSymbol(Factory* factory, Handle<Context> native_context,
                          const char* name, Handle<Symbol> value) {
@@ -4127,6 +4128,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_object_rest_spread_natives[] = {nullptr};
   static const char* harmony_async_iteration_natives[] = {nullptr};
   static const char* harmony_dynamic_import_natives[] = {nullptr};
+  static const char* harmony_template_escapes_natives[] = {nullptr};

[vogelheim, 2017/02/13 17:36:06]

Do we need this? Why? This feature doesn't seem to implement any natives.

--------------------

Background:
The original 'startup snapshot' could only be applied whole, and therefore the
snapshot couldn't contain any optional features. This initially worked fine for
--harmony-*, where the snapshot contained no 'harmony' features, and instead
they were added - if enabled - during initialization of the isolate, at some
additional runtime cost. When (most of) the --harmony-* features were turned on
by the default, this had the unfortunate effect that most of our users 'paid'
for the extra initialization. That's when the snapshot was extended to allow for
additional sections, one for each feature to be [en|dis]abled. This is the
mechanism you're extending here.

But... does this feature have any representation in the snapshot at all? I'd
think it's purely a parser issue.

[adamk, 2017/02/13 19:14:10]

This is needed to let the macro just below work. Agreed that we can probably get
rid of this soon, as we phase out experimental natives, but for now this is just
a bit of boilerplate with negligible runtime overhead.

 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {