add print to pdf for headless

components/printing/renderer/print_web_view_helper.cc

Index: components/printing/renderer/print_web_view_helper.cc
diff --git a/components/printing/renderer/print_web_view_helper.cc b/components/printing/renderer/print_web_view_helper.cc
index 2639579cdde4e3e4e5e9af793b18f138d551fc26..381692486f5153f3fe1c09adc44cdd46c48bf653 100644
--- a/components/printing/renderer/print_web_view_helper.cc
+++ b/components/printing/renderer/print_web_view_helper.cc
@@ -896,6 +896,12 @@ bool PrintWebViewHelper::Delegate::IsScriptedPrintEnabled() {
   return true;
 }
 
+#if defined(OS_MACOSX)
+bool PrintWebViewHelper::Delegate::UseSingleMetafile() {
+  return false;
+}
+#endif
+
 PrintWebViewHelper::PrintWebViewHelper(content::RenderFrame* render_frame,
                                        std::unique_ptr<Delegate> delegate)
     : content::RenderFrameObserver(render_frame),