Print preview not showing if default print is invalid.

chrome/renderer/mock_printer.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/mock_printer.h"
 
 #include "base/basictypes.h"
 #include "base/file_util.h"
 #include "base/shared_memory.h"
 #include "base/string16.h"
@@ skipping 69 matching lines @@
   page_size_ = params.page_size;
   printable_size_ = params.printable_size;
   margin_left_ = params.margin_left;
   margin_top_ = params.margin_top;
   display_header_footer_ = params.display_header_footer;
   date_ = params.date;
   title_ = params.title;
   url_ = params.url;
 }
 
+void MockPrinter::UseInvalidSettings() {
+  use_invalid_settings_ = true;
+  PrintMsg_Print_Params empty_param;
+  SetDefaultPrintSettings(empty_param);
+}
+
 void MockPrinter::ScriptedPrint(int cookie,
                                 int expected_pages_count,
                                 bool has_selection,
                                 PrintMsg_PrintPages_Params* settings) {
   // Verify the input parameters.
   EXPECT_EQ(document_cookie_, cookie);
 
   settings->Reset();
 
   settings->params.dpi = dpi_;
@@ skipping 129 matching lines @@
 bool MockPrinter::SaveBitmap(
     unsigned int page, const FilePath& filepath) const {
   if (printer_status_ != PRINTER_READY || page >= pages_.size())
     return false;
 
   pages_[page]->image().SaveToPng(filepath);
   return true;
 }
 
 int MockPrinter::CreateDocumentCookie() {
-  return ++current_document_cookie_;
+  return use_invalid_settings_ ? 0 : ++current_document_cookie_;
 }
 
 void MockPrinter::SetPrintParams(PrintMsg_Print_Params* params) {
   params->dpi = dpi_;
   params->max_shrink = max_shrink_;
   params->min_shrink = min_shrink_;
   params->desired_dpi = desired_dpi_;
   params->selection_only = selection_only_;
   params->document_cookie = document_cookie_;
   params->page_size = page_size_;
   params->printable_size = printable_size_;
   params->margin_left = margin_left_;
   params->margin_top = margin_top_;
   params->is_first_request = is_first_request_;
   params->preview_request_id = preview_request_id_;
   params->display_header_footer = display_header_footer_;
   params->date = date_;
   params->title = title_;
   params->url = url_;
 }