nacl: Fixed freeing static memory on video quit.

src/video/nacl/SDL_naclvideo.c

@@ -81,7 +81,7 @@ static int NACL_Available(void) {
 static void NACL_DeleteDevice(SDL_VideoDevice *device) {
     SDL_VideoData *driverdata = (SDL_VideoData*) device->driverdata;
     driverdata->ppb_core->ReleaseResource((PP_Resource) driverdata->ppb_message_loop);
-    SDL_free(device->driverdata);
+    /* device->driverdata is not freed because it points to static memory */
     SDL_free(device);
 }