The slides are written from the point of view of XF86/X.org, where originally indirect GLX was implemented by Mesa SW rasterizer in X server and the X server kn

The slides are written from the point of view of XF86/X.org, where originally indirect GLX was implemented by Mesa SW rasterizer in X server and the X server knew mostly nothing about DRM state (For example Xsun supported accelerated indirect GLX since forever and it even worked reasonably over network) .AIGLX is what allows X server to use external libGL.so to implement indirect GLX, GLX_EXT_texture_from_pixmap is mostly unrelated, but was introduced to X.org as part of that.