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

chrome/browser/ui/views/certificate_viewer_win.cc

Index: chrome/browser/ui/views/certificate_viewer_win.cc
diff --git a/chrome/browser/ui/views/certificate_viewer_win.cc b/chrome/browser/ui/views/certificate_viewer_win.cc
index fa345391d1eb89c4dec3a0a3ba4532f566aa4c20..4c4fd8f5617b69992184b3d020e05a248f6ae409 100644
--- a/chrome/browser/ui/views/certificate_viewer_win.cc
+++ b/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);