gsk: Add a helper for converting textures

This is a simple helper that feed a GdkTexture
through a renderer and returns the resulting
texture. This will be used to convert dmabuf
textures to 'native' textures.

gsk/gskrenderer.c

@@ -684,3 +684,22 @@ gsk_renderer_set_debug_flags (GskRenderer   *renderer,
 
   priv->debug_flags = flags;
 }
+
+/* Feed a texture through a renderer and return the resulting 'native' texture. */
+GdkTexture *
+gsk_renderer_convert_texture (GskRenderer *self,
+                              GdkTexture  *texture)
+{
+  int width, height;
+  GskRenderNode *node;
+  GdkTexture *result;
+
+  width = gdk_texture_get_width (texture);
+  height = gdk_texture_get_height (texture);
+
+  node = gsk_texture_node_new (texture, &GRAPHENE_RECT_INIT (0, 0, width, height));
+  result = gsk_renderer_render_texture (self, node, &GRAPHENE_RECT_INIT (0, 0, width, height));
+  gsk_render_node_unref (node);
+
+  return result;
+}