Extracted MetafilePlayer interface from printing::MetafilePlayer.

printing/printing_context_linux.cc

Index: printing/printing_context_linux.cc
diff --git a/printing/printing_context_linux.cc b/printing/printing_context_linux.cc
index 926d4e2bdaee928f27b5305c6837aafdde10ae7c..8e23577ce8b826429a0571315da25be12230c281 100644
--- a/printing/printing_context_linux.cc
+++ b/printing/printing_context_linux.cc
@@ -59,9 +59,8 @@ void PrintingContextLinux::SetPdfPaperSizeFunction(
   get_pdf_paper_size_ = get_pdf_paper_size;
 }
 
-void PrintingContextLinux::PrintDocument(const Metafile* metafile) {
+void PrintingContextLinux::PrintDocument(const MetafilePlayer& metafile) {
   DCHECK(print_dialog_);
-  DCHECK(metafile);
   print_dialog_->PrintDocument(metafile, document_name_);
 }