[es6] Re-implement rest parameters via desugaring.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 4a3dd2710b1514dcf0c179575a2e5420c132cfde..6effe1c3967686630218dbf00602bca2e010eb88 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -4658,12 +4658,6 @@ void HOptimizedGraphBuilder::SetUpScope(Scope* scope) {
     environment()->Bind(scope->arguments(), graph()->GetArgumentsObject());
   }
 
-  int rest_index;
-  Variable* rest = scope->rest_parameter(&rest_index);
-  if (rest) {
-    return Bailout(kRestParameter);
-  }
-
   if (scope->this_function_var() != nullptr ||
       scope->new_target_var() != nullptr) {
     return Bailout(kSuperReference);