add print to pdf for headless

headless/lib/browser/headless_print_manager.h

Index: headless/lib/browser/headless_print_manager.h
diff --git a/headless/lib/browser/headless_print_manager.h b/headless/lib/browser/headless_print_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..0b802e4c71349ec45a7d5847f31b87679806463b
--- /dev/null
+++ b/headless/lib/browser/headless_print_manager.h
@@ -0,0 +1,77 @@
+// Copyright (c) 2017 The Chromium Authors. All rights reserved.

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

no "(c)"

[jzfeng, 2017/03/29 03:50:13]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef HEADLESS_LIB_BROWSER_HEADLESS_PRINT_MANAGER_H_
+#define HEADLESS_LIB_BROWSER_HEADLESS_PRINT_MANAGER_H_
+
+#include <memory>
+#include <string>
+
+#include "components/printing/browser/print_manager.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+struct PrintHostMsg_DidPrintPage_Params;
+
+namespace printing {
+
+class HeadlessPrintManager
+    : public PrintManager,
+      public content::WebContentsUserData<HeadlessPrintManager> {
+ public:
+  ~HeadlessPrintManager() override;
+
+  enum PrintResult {

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

nit: This and the callback defintion goes first, per style guide.

[jzfeng, 2017/03/29 03:50:13]

Done.

+    kPrintSuccess,
+    kPrintingFailed,
+    kInvalidPrinterSettings,
+    kInvalidMemoryHandle,
+    kMetafileMapError,
+    kUnexpectedValidMemoryHandle,
+    kMetafileInvalidHeader,
+    kMetafileGetDataError,
+    kDuplicatedPrintingError,
+  };
+
+  using GetPDFCallback = base::Callback<void(PrintResult, const std::string&)>;
+  // Prints the current document immediately. Since the rendering is
+  // asynchronous, the actual printing will not be completed on the return of
+  // this function. Returns false if printing is impossible at the moment.
+  bool GetPDFContents(content::RenderFrameHost* rfh, GetPDFCallback callback);

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

nit: Pass callbacks by const-ref here too.

[jzfeng, 2017/03/29 03:50:13]

Done.

+  static std::string PrintResultToErrMsg(PrintResult result);
+  static std::unique_ptr<base::DictionaryValue> PDFContentsToDictionaryValue(
+      const std::string& data);
+
+ private:
+  explicit HeadlessPrintManager(content::WebContents* web_contents);
+  friend class content::WebContentsUserData<HeadlessPrintManager>;

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

nit: friends first in this section.

[jzfeng, 2017/03/29 03:50:13]

I see both content/public/browser/web_contents_user_data.h and
/chrome/browser/printing/print_view_manager.h put friend after the explicit
constructor. 
I feel a bit confused.

[Lei Zhang, 2017/03/29 05:30:15]

I guess it doesn't matter since
https://google.github.io/styleguide/cppguide.html#Declaration_Order now doesn't
say anything about friends. Previously, it just said they should be private.

+
+  // content::WebContentsObserver implementation.
+  bool OnMessageReceived(const IPC::Message& message,
+                         content::RenderFrameHost* render_frame_host) override;
+
+  // IPC Message handlers.
+  void OnGetDefaultPrintSettings(IPC::Message* reply_msg);
+  void OnShowInvalidPrinterSettingsError();
+  void OnPrintingFailed(int cookie) override;
+  void OnDidPrintPage(const PrintHostMsg_DidPrintPage_Params& params);
+
+  void ReleaseJob(PrintResult result);
+
+  content::RenderFrameHost* printing_rfh_;
+  GetPDFCallback callback_;
+  std::string data_;
+  bool is_active_;
+
+#if !defined(OS_MACOSX)
+  // Set to true when OnDidPrintPage() should be expecting the first page.
+  bool expecting_first_page_;
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(HeadlessPrintManager);
+};
+
+}  // namespace printing
+
+#endif  // HEADLESS_LIB_BROWSER_HEADLESS_PRINT_MANAGER_H_