renderer: Add API to check whether renderer is hardware accelerated

Also expose an introspected variant via the MetaBackend.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/838

src/backends/meta-backend.c

@@ -1032,6 +1032,21 @@ meta_backend_get_remote_access_controller (MetaBackend *backend)
 #endif
 }
 
+/**
+ * meta_backend_is_rendering_hardware_accelerated:
+ * @backend: A #MetaBackend
+ *
+ * Returns: %TRUE if the rendering is hardware accelerated, otherwise
+ * %FALSE.
+ */
+gboolean
+meta_backend_is_rendering_hardware_accelerated (MetaBackend *backend)
+{
+  MetaRenderer *renderer = meta_backend_get_renderer (backend);
+
+  return meta_renderer_is_hardware_accelerated (renderer);
+}
+
 /**
  * meta_backend_grab_device: (skip)
  */