Print preview page selection should not require a rerendering of draft pages.

chrome/browser/printing/print_preview_data_service.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/browser/printing/print_preview_data_service.h"
 
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/singleton.h"
 #include "printing/print_job_constants.h"
 
@@ skipping 31 matching lines @@
   // Set/Update the preview data entry for the specified |index|.
   void SetPreviewDataForIndex(int index, const RefCountedBytes* data) {
     if (index != printing::COMPLETE_PREVIEW_DOCUMENT_INDEX &&
         index < printing::FIRST_PAGE_INDEX) {
       return;
     }
 
     page_data_map_[index] = const_cast<RefCountedBytes*>(data);
   }
 
+  // Returns true if the draft pages is available.
+  bool IsDraftPagesAvailable(int draft_page_count) {
+    int page_data_map_size = page_data_map_.size();
+    return (page_data_map_size > draft_page_count ||
+            (page_data_map_size == draft_page_count &&
+             (page_data_map_.find(printing::COMPLETE_PREVIEW_DOCUMENT_INDEX) ==
+              page_data_map_.end())));
+  }
+
  private:
   friend class base::RefCounted<PrintPreviewDataStore>;
 
   // 1:1 relationship between page index and its associated preview data.
   // Key: Page index is zero-based and can be
   // |printing::COMPLETE_PREVIEW_DOCUMENT_INDEX| to represent complete preview
   // document.
   // Value: Preview data.
   typedef std::map<int, scoped_refptr<RefCountedBytes> > PreviewPageDataMap;
 
@@ skipping 36 matching lines @@
   data_store_map_[preview_ui_addr_str]->SetPreviewDataForIndex(index,
                                                                data_bytes);
 }
 
 void PrintPreviewDataService::RemoveEntry(
     const std::string& preview_ui_addr_str) {
   PreviewDataStoreMap::iterator it = data_store_map_.find(preview_ui_addr_str);
   if (it != data_store_map_.end())
     data_store_map_.erase(it);
 }
+
+bool PrintPreviewDataService::IsDraftPagesAvailable(
+    const std::string& preview_ui_addr_str,
+    int draft_page_count) {
+  if (data_store_map_.find(preview_ui_addr_str) != data_store_map_.end()) {
+    return data_store_map_[preview_ui_addr_str]->IsDraftPagesAvailable(
+        draft_page_count);
+  }
+  return false;
+}