The latest extension proposed for the OpenGL / OpenGL ES registry is INTEL_blackhole_render.

This Intel-developed blackhole render extension is quite simple: it's just about disabling the rendering to the GPU by an application.

The purpose of this extension is to allow an application to disable all rendering operations emitted to the GPU through the OpenGL rendering commands (Draw*, DispatchCompute*, BlitFramebuffer, etc...). Changes to the OpenGL pipeline are not affected.

It's currently waiting to be pulled if approved for the GL/GLES registry. The developers didn't comment on their intentions with this extension and searching around for INTEL_blackhole_render so far isn't revealing any other indications for this fairly straight-forward extension.