PrintPreview: Preview generation should not block print button.

chrome/browser/printing/print_preview_message_handler.cc

Index: chrome/browser/printing/print_preview_message_handler.cc
diff --git a/chrome/browser/printing/print_preview_message_handler.cc b/chrome/browser/printing/print_preview_message_handler.cc
index d293d6f1d6e2829f2f43e1e7e3964fb66a627179..551d67a02d1201e7d9d7f72da658fd07a1e30d56 100644
--- a/chrome/browser/printing/print_preview_message_handler.cc
+++ b/chrome/browser/printing/print_preview_message_handler.cc
@@ -6,6 +6,7 @@
 
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/browser_process.h"
+#include "chrome/browser/printing/background_printing_manager.h"
 #include "chrome/browser/printing/print_job_manager.h"
 #include "chrome/browser/printing/print_preview_tab_controller.h"
 #include "chrome/browser/printing/print_view_manager.h"
@@ -114,7 +115,19 @@ void PrintPreviewMessageHandler::OnPrintPreviewFailed(int document_cookie) {
   // User might have closed it already.
   if (!print_preview_tab)
     return;
-  print_preview_tab->web_ui()->CallJavascriptFunction("printPreviewFailed");
+
+  TabContentsWrapper* wrapper =
+      TabContentsWrapper::GetCurrentWrapperForContents(print_preview_tab);
+
+  if (g_browser_process->background_printing_manager()->
+          HasTabContents(wrapper)) {
+    // Preview tab was hidden to serve the print request.
+    delete wrapper;
+  } else {
+    PrintPreviewUI* print_preview_ui =
+      static_cast<PrintPreviewUI*>(print_preview_tab->web_ui());
+    print_preview_ui->CallJavascriptFunction("printPreviewFailed");
+  }
 }
 
 bool PrintPreviewMessageHandler::OnMessageReceived(