Print Preview: Display a throbber when the user requests the system print

chrome/browser/ui/webui/print_preview_ui.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_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_UI_H_
 #pragma once
 
 #include <string>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/time.h"
 #include "chrome/browser/printing/print_preview_data_service.h"
 #include "chrome/browser/ui/webui/chrome_web_ui.h"
 
 class PrintPreviewDataService;
+class PrintPreviewHandler;
 
 class PrintPreviewUI : public ChromeWebUI {
  public:
   explicit PrintPreviewUI(TabContents* contents);
   virtual ~PrintPreviewUI();
 
   // Gets the print preview |data|. The data is valid as long as the
   // PrintPreviewDataService is valid and SetPrintPreviewData() does not get
   // called.
   void GetPrintPreviewData(scoped_refptr<RefCountedBytes>* data);
 
   // Sets the print preview |data|.
   void SetPrintPreviewData(const RefCountedBytes* data);
 
   // Notify the Web UI renderer that preview data is available.
   // |expected_pages_count| specifies the total number of pages.
   // |job_title| is the title of the page being previewed.
   // |modifiable| indicates if the preview can be rerendered with different
   // print settings.
   void OnPreviewDataIsAvailable(int expected_pages_count,
                                 const string16& job_title,
                                 bool modifiable);
 
+  // Notify the Web UI that a navigation has occurred in this tab. This is the
+  // last chance to communicate with the source tab before the assocation is
+  // erased.
+  void OnNavigation();
+
   // Notify the Web UI that initiator tab is closed, so we can disable all
   // the controls that need the initiator tab for generating the preview data.
   // |initiator_tab_url| is passed in order to display a more accurate error
   // message.
   void OnInitiatorTabClosed(const std::string& initiator_tab_url);
 
   // Notify the Web UI renderer that file selection has been cancelled.
   void OnFileSelectionCancelled();
 
  private:
   // Helper function
   PrintPreviewDataService* print_preview_data_service();
 
   base::TimeTicks initial_preview_start_time_;
 
   // Store the PrintPreviewUI address string.
   std::string preview_ui_addr_str_;
 
+  // Weak pointer to the WebUI handler.
+  PrintPreviewHandler* handler_;
+
   DISALLOW_COPY_AND_ASSIGN(PrintPreviewUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_UI_H_