[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 b5c4eabf7a95010a9d94948abe36b1a1e0cb603c..bbea0fd62dc1aa7ad354094e3b4f23260564c142 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -4649,12 +4649,6 @@ void HOptimizedGraphBuilder::SetUpScope(Scope* scope) {
                         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);
@@ -5692,6 +5686,11 @@ void HOptimizedGraphBuilder::VisitVariableProxy(VariableProxy* expr) {
 }
 
 
+void HOptimizedGraphBuilder::VisitRestParameter(RestParameter* node) {
+  UNREACHABLE();
+}
+
+
 void HOptimizedGraphBuilder::VisitLiteral(Literal* expr) {
   DCHECK(!HasStackOverflow());
   DCHECK(current_block() != NULL);