Bug 1718131 - Close GdkDisplay in XREMain destructor. r=stransky

Differential Revision: https://phabricator.services.mozilla.com/D118753

toolkit/xre/nsAppRunner.cpp

@@ -3383,6 +3383,12 @@ class XREMain {
   ~XREMain() {
     mScopedXPCOM = nullptr;
     mAppData = nullptr;
+#if defined(MOZ_WIDGET_GTK)
+    if (mGdkDisplay) {
+      gdk_display_close(mGdkDisplay);
+      mGdkDisplay = nullptr;
+    }
+#endif
   }
 
   int XRE_main(int argc, char* argv[], const BootstrapConfig& aConfig);