Currently, webrender could resolve a gl texture id from a external texture id through the externalImage callback api[1]. Then, webrender could use that gl texture id for rendering. We could also pass a shmem or raw buffer to webrender, and let webrender to upload this buffer into gl texture. In this way, webrender might use texture atlas for this texture uploading. That could have a better performance in drawing. We can't just use the wr_add_image() api directly, that api implies some memory copy operations. That's not a good practice for a large image. [1] https://github.com/servo/webrender/pull/636/commits/1cb9ab2ade29d210cc9b04eac5ac5cec57ecb206

PR: https://github.com/servo/webrender/pull/776

The pr is merged.