This state tracker is intended to implement VA-API, the Video Acceleration API, using shaders within Gallium3D for handling the video decoding process rather than the CPU. The VA-API state tracker didn't make use of the Radeon UVD engine or any discrete video decoding hardware. However, like yesterday's disabling of the Direct3D 10/11 state tracker for Gallium3D, this state tracker too is in a poor state.
However, rather than just disabling the build support for VA-API in Mesa, it's set to be removed entirely. Matt Turner sent in a patch to remove the 1.5k lines of code for this "VA" state tracker that had targets for the R300 and R600 Gallium3D hardware drivers.
The removal of the video acceleration Gallium3D state tracker doesn't affect Intel's usage of VA-API by their Mesa DRI driver and the separate VA-API library/driver status, which is still in great shape and makes use of Intel's dedicated video hardware.
The patch, which is likely to be merged to Mesa Git master, can be found on the mesa-dev mailing list.
While VA-API may be going away, at least there's the VDPAU state tracker that's still around and slightly more maintained and useful. The VDPAU state tracker is also making use of shaders for video decoding using NVIDIA's Video Decode and Presentation API for Unix.