  This paper discusses the in-domain feedback stabilization of
reaction-diffusion PDEs with Robin boundary conditions in the presence of an
uncertain time- and spatially-varying delay in the distributed actuation. The
proposed control design strategy consists of a constant-delay predictor
feedback designed based on the known nominal value of the control input delay
and is synthesized on a finite-dimensional truncated model capturing the
unstable modes of the original infinite-dimensional system. By using a
small-gain argument, we show that the resulting closed-loop system is
exponentially stable provided that the variations of the delay around its
nominal value are small enough. The proposed proof actually applies to any
distributed-parameter system associated with an unbounded operator that 1)
generates a $C_0$-semigroup on a weighted space of square integrable functions
over a compact interval; and 2) is self-adjoint with compact resolvent.
