Print preview: Display a dummy page when a user visits chrome://print directly.

chrome/browser/ui/webui/print_preview_data_source.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_DATA_SOURCE_H_
 #define CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_DATA_SOURCE_H_
 #pragma once
 
 #include <string>
 
@@ skipping 12 matching lines @@
 //                  |printing::COMPLETE_PREVIEW_DOCUMENT_INDEX| to represent
 //                  a print ready PDF.
 //
 // Example:
 //    chrome://print/0xab0123ef/10/print.pdf
 //
 // Requests to chrome://print with paths not ending in /print.pdf are used
 // to return the markup or other resources for the print preview page itself.
 class PrintPreviewDataSource : public ChromeWebUIDataSource {
  public:
-  PrintPreviewDataSource();
+  explicit PrintPreviewDataSource(bool is_dummy);
 
   // ChromeURLDataManager::DataSource implementation.
   virtual void StartDataRequest(const std::string& path,
                                 bool is_incognito,
                                 int request_id) OVERRIDE;
  private:
   virtual ~PrintPreviewDataSource();
+  void Init(bool is_dummy);
 
   DISALLOW_COPY_AND_ASSIGN(PrintPreviewDataSource);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_DATA_SOURCE_H_