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

In preference to https://codereview.chromium.org/61093002/.

R=sky@chromium.org
BUG=306295

Review URL: https://codereview.chromium.org/59613009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233332 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/views/certificate_viewer_win.cc

@@ -9,6 +9,7 @@
 #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)
@@ -40,6 +41,11 @@ void ShowCertificateViewerImpl(content::WebContents* web_contents,
   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);