add print to pdf for headless

headless/lib/renderer/headless_print_web_view_helper_delegate.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 HEADLESS_LIB_RENDERER_HEADLESS_PRINT_WEB_VIEW_HELPER_DELEGATE_H_
+#define HEADLESS_LIB_RENDERER_HEADLESS_PRINT_WEB_VIEW_HELPER_DELEGATE_H_
+
+#include "components/printing/renderer/print_web_view_helper.h"
+
+namespace headless {
+
+class HeadlessPrintWebViewHelperDelegate
+    : public printing::PrintWebViewHelper::Delegate {
+ public:
+  ~HeadlessPrintWebViewHelperDelegate() override;

[Lei Zhang, 2017/03/29 01:38:04]

Provide a ctor.

[jzfeng, 2017/03/29 03:50:14]

Done.

+
+  bool CancelPrerender(content::RenderFrame* render_frame) override;

[Lei Zhang, 2017/03/29 01:38:04]

nit: Bundle the override methods together. e.g.

class Foo : public Bar {
 public:
  Foo();
  ~Foo() override;

  // Bar:
  BarMethod1(...) override;
  ...
  BarMethodN(...) override;

  NotOverrideMethod(...);
  ...
};

[jzfeng, 2017/03/29 03:50:14]

Done.

+
+  blink::WebElement GetPdfElement(blink::WebLocalFrame* frame) override;
+
+  bool IsPrintPreviewEnabled() override;
+
+  bool OverridePrint(blink::WebLocalFrame* frame) override;
+
+  bool IsAskPrintSettingsEnabled() override;
+};
+}
+#endif  // HEADLESS_LIB_RENDERER_HEADLESS_PRINT_WEB_VIEW_HELPER_DELEGATE_H_