  Quasar microlensing analyses implicitly generate a model of the variability
of the source quasar. The implied source variability may be unrealistic yet its
likelihood is generally not evaluated. We used the damped random walk (DRW)
model for quasar variability to evaluate the likelihood of the source
variability and applied the revised algorithm to a microlensing analysis of the
lensed quasar RX J1131-1231. We compared the estimates of the source quasar
disk and average lens galaxy stellar mass with and without applying the DRW
likelihoods for the source variability model and found no significant effect on
the estimated physical parameters. The most likely explanation is that
unreliastic source light curve models are generally associated with poor
microlensing fits that already make a negligible contribution to the
probability distributions of the derived parameters.
