add print to pdf for headless

components/printing/renderer/print_web_view_helper_mac.mm

Index: components/printing/renderer/print_web_view_helper_mac.mm
diff --git a/components/printing/renderer/print_web_view_helper_mac.mm b/components/printing/renderer/print_web_view_helper_mac.mm
index 6de15ad3c7a8f111a839fde82925a3f96b82bd22..84f9f91538fcf6ef36215b7f3aaacdf2822e88ef 100644
--- a/components/printing/renderer/print_web_view_helper_mac.mm
+++ b/components/printing/renderer/print_web_view_helper_mac.mm
@@ -30,30 +30,35 @@ bool PrintWebViewHelper::PrintPagesNative(blink::WebLocalFrame* frame,
 
   PrintMsg_PrintPage_Params page_params;
   page_params.params = print_params;
-  for (int page_number : printed_pages) {
-    page_params.page_number = page_number;
-    PrintPageInternal(page_params, frame);
+
+  if (delegate_->UseSingleMetafile()) {
+    PrintPagesInternal(page_params, frame, printed_pages);
+    return true;
   }
+
+  for (int page_number : printed_pages)
+    PrintPagesInternal(page_params, frame, std::vector<int>{page_number});
   return true;
 }
 #endif  // BUILDFLAG(ENABLE_BASIC_PRINTING)
 
-void PrintWebViewHelper::PrintPageInternal(
+void PrintWebViewHelper::PrintPagesInternal(
     const PrintMsg_PrintPage_Params& params,
-    blink::WebLocalFrame* frame) {
+    blink::WebLocalFrame* frame,
+    std::vector<int> printed_pages) {
   PdfMetafileSkia metafile(PDF_SKIA_DOCUMENT_TYPE);
   CHECK(metafile.Init());
 
-  int page_number = params.page_number;
   gfx::Size page_size_in_dpi;
   gfx::Rect content_area_in_dpi;

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

In principle, due to fancy CSS, this can be different per page. e.g.
https://www.smashingmagazine.com/2015/01/designing-for-print-with-css/#left-a...

Though I haven't actually tried this and I don't know how well we actually
support it.

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

I feel it is ok to leave as is?

For the normal case, the size of printed_pages is always one, so the code won't
change anything. These two thing can still be different for each page.

For the headless case, the page size and content area is not used by the print
manager. So I guess it won't matter.

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

That assumes nobody else will try to use UseSingleMetafile(). Since we can't
always predict the future, and this is a subtle difference that most readers
won't notice by just glancing at the code, can we leave a comment here to
describe the potential bug?

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

Done. Added this potential bug to the comment of the UseSingleMetafile method.

-  RenderPage(print_pages_params_->params, page_number, frame, false, &metafile,
-             &page_size_in_dpi, &content_area_in_dpi);
+  for (int page_number : printed_pages) {
+    RenderPage(params.params, page_number, frame, false, &metafile,
+               &page_size_in_dpi, &content_area_in_dpi);
+  }
   metafile.FinishDocument();
 
   PrintHostMsg_DidPrintPage_Params page_params;
   page_params.data_size = metafile.GetDataSize();
-  page_params.page_number = page_number;
   page_params.document_cookie = params.params.document_cookie;
   page_params.page_size = page_size_in_dpi;
   page_params.content_area = content_area_in_dpi;
@@ -65,7 +70,11 @@ void PrintWebViewHelper::PrintPageInternal(
     page_params.data_size = 0;
   }
 
-  Send(new PrintHostMsg_DidPrintPage(routing_id(), page_params));
+  for (int page_number : printed_pages) {
+    page_params.page_number = page_number;
+    Send(new PrintHostMsg_DidPrintPage(routing_id(), page_params));
+    page_params.metafile_data_handle = base::SharedMemoryHandle();
+  }
 }
 
 #if BUILDFLAG(ENABLE_PRINT_PREVIEW)