[es6] Fix scoping for default parameters in arrow functions

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 26c092fe3e4d16f8dfbd86eaf172710c645e2123..6ac80f88201bbd906ae9487be0948f92d966d0b2 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -178,13 +178,19 @@ class Scope: public ZoneObject {
     return proxy;
   }
 
+  void AddUnresolved(VariableProxy* proxy) {
+    DCHECK(!already_resolved());
+    DCHECK(!proxy->is_resolved());
+    unresolved_.Add(proxy, zone_);
+  }
+
   // Remove a unresolved variable. During parsing, an unresolved variable
   // may have been added optimistically, but then only the variable name
   // was used (typically for labels). If the variable was not declared, the
   // addition introduced a new unresolved variable which may end up being
   // allocated globally as a "ghost" variable. RemoveUnresolved removes
   // such a variable again if it was added; otherwise this is a no-op.
-  void RemoveUnresolved(VariableProxy* var);
+  bool RemoveUnresolved(VariableProxy* var);
 
   // Creates a new temporary variable in this scope's TemporaryScope.  The
   // name is only used for printing and cannot be used to find the variable.
@@ -459,6 +465,7 @@ class Scope: public ZoneObject {
 
   // The scope immediately surrounding this scope, or NULL.
   Scope* outer_scope() const { return outer_scope_; }
+  void set_outer_scope(Scope* outer_scope) { outer_scope_ = outer_scope; }
 
   // The ModuleDescriptor for this scope; only for module scopes.
   ModuleDescriptor* module() const { return module_descriptor_; }