Bug 1485616 - [Wayland] Wait with drawing until mozcontainer init is finished, r=jhorak

Differential Revision: https://phabricator.services.mozilla.com/D14070

--HG--
extra : moz-landing-system : lando

widget/gtk/mozcontainer.cpp

@@ -156,7 +156,8 @@ void moz_container_init(MozContainer *container) {
   container->subsurface = nullptr;
   container->eglwindow = nullptr;
   container->frame_callback_handler = nullptr;
-  container->ready_to_draw = false;
+  // We can draw to x11 window any time.
+  container->ready_to_draw = GDK_IS_X11_DISPLAY(gdk_display_get_default());
   container->surface_needs_clear = true;
 #endif
 }

widget/gtk/nsWindow.cpp

@@ -1869,6 +1869,9 @@ gboolean nsWindow::OnExposeEvent(cairo_t *cr) {
 
   // Windows that are not visible will be painted after they become visible.
   if (!mGdkWindow || mIsFullyObscured || !mHasMappedToplevel) return FALSE;
+#ifdef MOZ_WAYLAND
+  if (mContainer && !mContainer->ready_to_draw) return FALSE;
+#endif
 
   nsIWidgetListener *listener = GetListener();
   if (!listener) return FALSE;