Print Preview: Make preview generation event driven to eliminate synchronous messages.

chrome/browser/ui/webui/print_preview_handler.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/ui/webui/print_preview_handler.h"
 
 #include <string>
 
 #include "base/base64.h"
 #if !defined(OS_CHROMEOS)
@@ skipping 809 matching lines @@
 }
 
 void PrintPreviewHandler::OnNavigation() {
   TabContents* initiator_tab = GetInitiatorTab();
   if (!initiator_tab)
     return;
 
   TabContentsWrapper* wrapper =
       TabContentsWrapper::GetCurrentWrapperForContents(initiator_tab);
   wrapper->print_view_manager()->set_observer(NULL);
+
+  // Tell the initiator tab to stop rendering the print preview, if any,
+  // since the preview tab is gone.
+  RenderViewHost* rvh = initiator_tab->render_view_host();
+  rvh->Send(new PrintMsg_AbortPreview(rvh->routing_id()));
 }
 
 void PrintPreviewHandler::FileSelected(const FilePath& path,
                                        int index, void* params) {
   PrintPreviewUI* print_preview_ui = static_cast<PrintPreviewUI*>(web_ui_);
   scoped_refptr<RefCountedBytes> data(new RefCountedBytes());
   print_preview_ui->GetPrintPreviewData(&data);
   if (!data->front()) {
     NOTREACHED();
     return;
@@ skipping 30 matching lines @@
     return;
 
   // We no longer require the initiator tab details. Remove those details
   // associated with the preview tab to allow the initiator tab to create
   // another preview tab.
   printing::PrintPreviewTabController* tab_controller =
      printing::PrintPreviewTabController::GetInstance();
   if (tab_controller)
     tab_controller->EraseInitiatorTabInfo(preview_tab());
 }