Bug 973192 - call XSync instead of XCloseDisplay unless NS_FREE_PERMANENT_DATA is defined - r=karlt

toolkit/xre/glxtest.cpp

@@ -229,7 +229,16 @@ static void glxtest()
   glXDestroyContext(dpy, context);
   XDestroyWindow(dpy, window);
   XFreeColormap(dpy, swa.colormap);
+
+#ifdef NS_FREE_PERMANENT_DATA // conditionally defined in nscore.h, don't forget to #include it above
   XCloseDisplay(dpy);
+#else
+  // This XSync call wanted to be instead:
+  //   XCloseDisplay(dpy);
+  // but this can cause 1-minute stalls on certain setups using Nouveau, see bug 973192
+  XSync(dpy, False);
+#endif
+
   dlclose(libgl);
 
   ///// Finally write data to the pipe