Reapply "Save and restore feedback from JIT."

runtime/vm/program_visitor.h

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef RUNTIME_VM_PROGRAM_VISITOR_H_
+#define RUNTIME_VM_PROGRAM_VISITOR_H_
+
+#include "vm/allocation.h"
+
+namespace dart {
+
+class Function;
+class Class;
+
+template <typename T>
+class Visitor : public ValueObject {
+ public:
+  virtual ~Visitor() {}
+  virtual void Visit(const T& obj) = 0;
+};
+
+typedef Visitor<Function> FunctionVisitor;
+typedef Visitor<Class> ClassVisitor;
+
+class ProgramVisitor : public AllStatic {
+ public:
+  static void VisitFunctions(FunctionVisitor* visitor);
+  static void VisitClasses(ClassVisitor* visitor);
+};
+
+}  // namespace dart
+
+#endif  // RUNTIME_VM_PROGRAM_VISITOR_H_