Linux: cefclient: Fix crash when creating popup window (issue #2512)

tests/cefclient/browser/browser_window_std_gtk.cc

@@ -162,7 +162,7 @@ void BrowserWindowStdGtk::Hide() {
 void BrowserWindowStdGtk::SetBounds(int x, int y, size_t width, size_t height) {
   REQUIRE_MAIN_THREAD();
 
-  if (browser_) {
+  if (xdisplay_ && browser_) {
     ::Window xwindow = browser_->GetHost()->GetWindowHandle();
     DCHECK(xwindow);
     SetXWindowBounds(xdisplay_, xwindow, x, y, width, height);

tests/cefclient/browser/root_window_gtk.cc

@@ -369,6 +369,7 @@ void RootWindowGtk::CreateRootWindow(const CefBrowserSettings& settings,
 
   // Set the Display associated with the browser.
   ::Display* xdisplay = GDK_WINDOW_XDISPLAY(gtk_widget_get_window(window_));
+  CHECK(xdisplay);
   if (with_osr_) {
     static_cast<BrowserWindowOsrGtk*>(browser_window_.get())
         ->set_xdisplay(xdisplay);