We used to swap in a buffer with (0,0,0,1) for all vertex colors for
drop shadows and outlines. However, this vertex buffer couldn't be
uploaded separately from the vertex data in OBS, so we were reuploading
the text vertices every frame.
Instead, let's use a uniform for this uniform data and save 500us (or
more when handles are visible), a significant portion of my test scenes
render time.
cfb10ece79