add print to pdf for headless

headless/lib/renderer/headless_content_renderer_client.h

Index: headless/lib/renderer/headless_content_renderer_client.h
diff --git a/headless/lib/renderer/headless_content_renderer_client.h b/headless/lib/renderer/headless_content_renderer_client.h
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+++ b/headless/lib/renderer/headless_content_renderer_client.h
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+// 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 HEADLESS_LIB_RENDERER_HEADLESS_CONTENT_RENDERER_CLIENT_H_
+#define HEADLESS_LIB_RENDERER_HEADLESS_CONTENT_RENDERER_CLIENT_H_
+
+#include "content/public/renderer/content_renderer_client.h"
+
+namespace headless {
+
+class HeadlessContentRendererClient : public content::ContentRendererClient {
+ public:
+  HeadlessContentRendererClient();
+  ~HeadlessContentRendererClient() override;
+
+ private:
+  void RenderFrameCreated(content::RenderFrame* render_frame) override;
+
+  DISALLOW_COPY_AND_ASSIGN(HeadlessContentRendererClient);
+};
+
+}  // namespace headless
+
+#endif  // HEADLESS_LIB_RENDERER_HEADLESS_CONTENT_RENDERER_CLIENT_H_