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

chrome/browser/ui/webui/print_preview_data_source.h

Index: chrome/browser/ui/webui/print_preview_data_source.h
===================================================================
--- chrome/browser/ui/webui/print_preview_data_source.h	(revision 114056)
+++ chrome/browser/ui/webui/print_preview_data_source.h	(working copy)
@@ -30,7 +30,7 @@
 // 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,
@@ -38,6 +38,7 @@
                                 int request_id) OVERRIDE;
  private:
   virtual ~PrintPreviewDataSource();
+  void Init(bool is_dummy);
 
   DISALLOW_COPY_AND_ASSIGN(PrintPreviewDataSource);
 };