Block nested system print dialogs on Windows

printing/printing_context_win.cc

 // Copyright (c) 2012 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 "printing/printing_context_win.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 341 matching lines @@
   DCHECK(!in_print_job_);
   settings_.set_device_name(device_name);
   PrintSettingsInitializerWin::InitPrintSettings(
       context_, *dev_mode, &settings_);
 
   return OK;
 }
 
 HWND PrintingContextWin::GetRootWindow(gfx::NativeView view) {
   HWND window = NULL;
-  if (view)
+  if (view && view->GetHost())
     window = view->GetHost()->GetAcceleratedWidget();
   if (!window) {
     // TODO(maruel):  crbug.com/1214347 Get the right browser window instead.
     return GetDesktopWindow();
   }
   return window;
 }
 
 scoped_ptr<DEVMODE, base::FreeDeleter> PrintingContextWin::ShowPrintDialog(
     HANDLE printer,
@@ skipping 18 matching lines @@
 
   if (canceled) {
     result.reset();
     abort_printing_ = true;
   }
 
   return result.Pass();
 }
 
 }  // namespace printing