Likely most notable of the OpenGL work that landed in LibreOffice today was the deferred and optimized (text) texture drawing. That change in particular should really help with LibreOffice's text rendering when using OpenGL.
As explained by Tomaz Vajngerl of Collabora, "Switching between textures is not cheap, so minimizing the amount of switching performs better. So instead of immediate drawing we can accumulate texture draw actions and defer drawing as long as possible. After that switch all accumulated textures and draw everything needed with one GL draw call."
There were also several other OpenGL fixes/improvements that landed today, including better packing of textures.
These improvements plus other changes and new features will be found in the LibreOffice 5.2 release. LibreOffice 5.2 is scheduled for release in early August.