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

chrome/browser/printing/print_preview_tab_controller.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_tab_controller.h"
 
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/sessions/restore_tab_helper.h"
 #include "chrome/browser/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/browser.h"
@@ skipping 120 matching lines @@
       return;
     }
   }
 
   if (source_tab_is_preview_tab) {
     // Remove the initiator tab's observers before erasing the mapping.
     TabContents* initiator_tab = GetInitiatorTab(source_tab);
     if (initiator_tab)
       RemoveObservers(initiator_tab);
 
+    PrintPreviewUI* print_preview_ui =
+        static_cast<PrintPreviewUI*>(source_tab->web_ui());

[Lei Zhang, 2011/06/28 20:55:35]

For the case of: open print preview; close initiator tab; click "reopen the
page", normally you would get NULL here and skip the OnNavigation() call.
However, if the initiator tab is a WebUI page, e.g. the NTP, then you would get
a WebUI back and incorrectly cast it to a PrintPreviewUI.

[Lei Zhang, 2011/06/28 20:58:04]

Probably just want to check with IsPrintPreviewTab(source_tab) here.

+    if (print_preview_ui)
+      print_preview_ui->OnNavigation();
+
     // Erase the map entry.
     preview_tab_map_.erase(source_tab);
   } else {
     // Initiator tab is closed. Disable the controls in preview tab.
     PrintPreviewUI* print_preview_ui =
         static_cast<PrintPreviewUI*>(preview_tab->web_ui());
     print_preview_ui->OnInitiatorTabClosed(source_tab->GetURL().spec());
 
     // |source_tab| is an initiator tab, update the map entry.
     preview_tab_map_[preview_tab] = NULL;
@@ skipping 78 matching lines @@
 }
 
 void PrintPreviewTabController::RemoveObservers(TabContents* tab) {
   registrar_.Remove(this, NotificationType::TAB_CONTENTS_DESTROYED,
                     Source<TabContents>(tab));
   registrar_.Remove(this, NotificationType::NAV_ENTRY_COMMITTED,
                     Source<NavigationController>(&tab->controller()));
 }
 
 }  // namespace printing