add print to pdf for headless

components/printing/renderer/print_web_view_helper.h

Index: components/printing/renderer/print_web_view_helper.h
diff --git a/components/printing/renderer/print_web_view_helper.h b/components/printing/renderer/print_web_view_helper.h
index d979333feb1fd72972fe4109e1afc061f49af2d1..3b3549531457d619ede75c0328b2c9d50bc87423 100644
--- a/components/printing/renderer/print_web_view_helper.h
+++ b/components/printing/renderer/print_web_view_helper.h
@@ -108,6 +108,10 @@ class PrintWebViewHelper
     // Returns true if printing is overridden and the default behavior should be
     // skipped for |frame|.
     virtual bool OverridePrint(blink::WebLocalFrame* frame) = 0;
+
+#if defined(OS_MACOSX)
+    virtual bool UseSingleMetafile();

[Lei Zhang, 2017/04/06 08:08:42]

Explain what this does.

[jzfeng, 2017/04/06 09:01:51]

Done.

+#endif
   };
 
   PrintWebViewHelper(content::RenderFrame* render_frame,
@@ -283,8 +287,9 @@ class PrintWebViewHelper
 
   // Prints the page listed in |params|.
 #if defined(OS_MACOSX)
-  void PrintPageInternal(const PrintMsg_PrintPage_Params& params,
-                         blink::WebLocalFrame* frame);
+  void PrintPagesInternal(const PrintMsg_PrintPage_Params& params,
+                          blink::WebLocalFrame* frame,
+                          std::vector<int> printed_pages);

[Lei Zhang, 2017/04/06 08:08:42]

Pass by const ref.

[jzfeng, 2017/04/06 09:01:51]

Done.

 #else
   void PrintPageInternal(const PrintMsg_PrintPage_Params& params,
                          blink::WebLocalFrame* frame,