We'd end up with the constant offset in the uniform stream anyway, since
they're bigger than small immediates.  Avoids the extra uniforms and adds
in the shader in favor of just adding once on the CPU.

shader-db:
total instructions in shared programs: 6496865 -> 6494851 (-0.03%)
total uniforms in shared programs: 2119511 -> 2117243 (-0.11%)