fix second window not painting on aura while cert dialog is open

chrome/browser/ui/views/certificate_viewer_win.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/certificate_viewer.h"
 
 #include <windows.h>
 #include <cryptuiapi.h>
 #pragma comment(lib, "cryptui.lib")
 
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
 #include "net/cert/x509_certificate.h"
 
 #if defined(USE_AURA)
 #include "chrome/browser/ui/host_desktop.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 #endif
 
 namespace {
 
@@ skipping 11 matching lines @@
   // in CryptUIDlgViewCertificate modal to the browser.
   view_info.hwndParent = parent;
   view_info.dwFlags = CRYPTUI_DISABLE_EDITPROPERTIES |
                       CRYPTUI_DISABLE_ADDTOSTORE;
   view_info.pCertContext = cert_list;
   HCERTSTORE cert_store = cert_list->hCertStore;
   view_info.cStores = 1;
   view_info.rghStores = &cert_store;
   BOOL properties_changed;
 
+  // We must allow nested tasks to dispatch so that, e.g. gpu tasks are
+  // processed for painting. This allows a second window to continue painting
+  // while the the certificate dialog is open.
+  base::MessageLoop::ScopedNestableTaskAllower allow(
+      base::MessageLoop::current());
   // This next call blocks but keeps processing windows messages, making it
   // modal to the browser window.
   BOOL rv = ::CryptUIDlgViewCertificate(&view_info, &properties_changed);
 
   CertFreeCertificateContext(cert_list);
 }
 
 }  // namespace
 
 #if defined(USE_AURA)
 void ShowCertificateViewer(content::WebContents* web_contents,
                            gfx::NativeWindow parent,
                            net::X509Certificate* cert) {
   if (chrome::GetHostDesktopTypeForNativeWindow(parent) !=
       chrome::HOST_DESKTOP_TYPE_ASH) {
     ShowCertificateViewerImpl(
         web_contents, parent->GetDispatcher()->GetAcceleratedWidget(), cert);
   } else {
     NOTIMPLEMENTED();
   }
 }
 #else
 void ShowCertificateViewer(content::WebContents* web_contents,
                            gfx::NativeWindow parent,
                            net::X509Certificate* cert) {
   ShowCertificateViewerImpl(web_contents, parent, cert);
 }
 #endif