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When this comment was written, it wasn't clear how the library was going to
figure out which back-end driver to load.  Since then, the wrapper has been
updated to make DRI2 that "VDPAU-specific X extension."
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: José Hiram Soltren <jsoltren@nvidia.com>