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..8b01268bbf6c348ed9ab25033ef1d2673263937f 100644
--- a/components/printing/renderer/print_web_view_helper.h
+++ b/components/printing/renderer/print_web_view_helper.h
@@ -108,6 +108,13 @@ 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)
+    // If true, all the printed pages are returned in the first
+    // PrintHostMsg_DidPrintPage metafile. This is the behavior in linux and
+    // windows.

[Lei Zhang, 2017/04/06 10:23:00]

It's good to capitalize Windows to distinguish it from windows. Might as well
for 'linux' for consistency.

[jzfeng, 2017/04/07 03:24:06]

Done.

+    virtual bool UseSingleMetafile();
+#endif
   };
 
   PrintWebViewHelper(content::RenderFrame* render_frame,
@@ -283,8 +290,9 @@ 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,
+                          const std::vector<int>& printed_pages);
 #else
   void PrintPageInternal(const PrintMsg_PrintPage_Params& params,
                          blink::WebLocalFrame* frame,