[es6] implement default/optional parameters (WIP / comments)

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index 93268ad31905015d78f014430124f70e6e7d1807..5b8c58fdc1a559100933bebe4ab91a8f7a2ffd24 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -452,12 +452,13 @@ Variable* Scope::Lookup(const AstRawString* name) {
 
 
 Variable* Scope::DeclareParameter(const AstRawString* name, VariableMode mode,
-                                  bool is_rest) {
+                                  ParameterKind kind) {
   DCHECK(!already_resolved());
   DCHECK(is_function_scope());
   Variable* var = variables_.Declare(this, name, mode, Variable::NORMAL,
                                      kCreatedInitialized);
-  if (is_rest) {
+  var->set_parameter_kind(kind);
+  if (kind.isRestParameter()) {
     DCHECK_NULL(rest_parameter_);
     rest_parameter_ = var;
     rest_index_ = num_parameters();