Print preview rendered pages count

During print preview user can choose a custom page range for printing.
This can easily be less than the entire document.  The recent change
for concurrent PDF composition [1] erroneously always expected the
full document to be collected, which fails with a hung preview if the
user selects a custom page range.

Correct this by updating the PrintRenderFrameHelper to pass along only
the number of pages rendered for the page selection.

[1] https://crrev.com/c/1917685

Bug: 1028104
Change-Id: Ic6ecbc09d09a8c7f30bc959b0a3808d66f1274ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935724Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Alan Screen <awscreen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719263}

components/printing/renderer/print_render_frame_helper.cc

@@ -1568,7 +1568,7 @@ bool PrintRenderFrameHelper::FinalizePrintReadyDocument() {
 
   preview_params.document_cookie = print_pages_params_->params.document_cookie;
   preview_params.expected_pages_count =
-      print_preview_context_.total_page_count();
+      print_preview_context_.pages_rendered_count();
 
   PrintHostMsg_PreviewIds ids(print_pages_params_->params.preview_request_id,
                               print_pages_params_->params.preview_ui_id);
@@ -2647,6 +2647,11 @@ PrintRenderFrameHelper::PrintPreviewContext::pages_to_render() const {
   return pages_to_render_;
 }
 
+int PrintRenderFrameHelper::PrintPreviewContext::pages_rendered_count() const {
+  DCHECK_EQ(DONE, state_);
+  return pages_to_render_.size();
+}
+
 MetafileSkia* PrintRenderFrameHelper::PrintPreviewContext::metafile() {
   DCHECK(IsRendering());
   return metafile_.get();

components/printing/renderer/print_render_frame_helper.h

@@ -524,6 +524,7 @@ class PrintRenderFrameHelper
 
     int total_page_count() const;
     const std::vector<int>& pages_to_render() const;
+    int pages_rendered_count() const;
     MetafileSkia* metafile();
     int last_error() const;