Refactor parser Checkpoints.

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index 4bc9b1d9ea3deb705c56ab76fc48297df5a2477b..4aa6f719f3b9361d7cf6a1622f4cc7cc8dd0f908 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -355,21 +355,6 @@ class ParserTraits {
     typedef Variable GeneratorVariable;
     typedef v8::internal::Zone Zone;
 
-    class Checkpoint BASE_EMBEDDED {
-     public:
-      template <typename Parser>
-      explicit Checkpoint(Parser* parser) {
-        isolate_ = parser->zone()->isolate();
-        saved_ast_node_id_ = isolate_->ast_node_id();
-      }
-
-      void Restore() { isolate_->set_ast_node_id(saved_ast_node_id_); }
-
-     private:
-      Isolate* isolate_;
-      int saved_ast_node_id_;
-    };
-
     typedef v8::internal::AstProperties AstProperties;
     typedef Vector<VariableProxy*> ParameterIdentifierVector;
 
@@ -388,6 +373,8 @@ class ParserTraits {
     typedef AstNodeFactory<AstConstructionVisitor> Factory;
   };
 
+  class Checkpoint;
+
   explicit ParserTraits(Parser* parser) : parser_(parser) {}
 
   // Custom operations executed when FunctionStates are created and destructed.