Introduce RenderFrameVisitor

content/public/renderer/render_frame_visitor.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_PUBLIC_RENDERER_RENDER_FRAME_VISITOR_H_
+#define CONTENT_PUBLIC_RENDERER_RENDER_FRAME_VISITOR_H_
+
+namespace content {
+
+class RenderFrame;
+
+class RenderFrameVisitor {
+ public:
+  // Return true to continue visiting RenderFrames or false to stop.
+  virtual bool Visit(RenderFrame* render_frame) = 0;
+
+ protected:
+  virtual ~RenderFrameVisitor() {}
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_RENDERER_RENDER_FRAME_VISITOR_H_