[es6] re-implement rest parameters via desugaring

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index 41622894a122d5a844788223bcc757f121585009..e999f23f4148afda440d45ef168509dfe69fe86a 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -772,6 +772,15 @@ Scope* Scope::DeclarationScope() {
 }
 
 
+Scope* Scope::TempScope() {
+  Scope* scope = this;
+  while (!scope->is_declaration_scope() || scope->is_block_scope()) {
+    scope = scope->outer_scope();
+  }
+  return scope;
+}
+
+
 Handle<ScopeInfo> Scope::GetScopeInfo(Isolate* isolate) {
   if (scope_info_.is_null()) {
     scope_info_ = ScopeInfo::Create(isolate, zone(), this);