In the reaction of aluminum bromide with ionized sodium bromide, which compound is the Lewis acid?

$A l B {r}_{3} + B {r}^{-} \rightarrow A l B {r}_{4}^{-}$,
clearly the bromide ion is the base, the electron donor, and aluminum, the acid, the electron-pair acceptor. How would you designate the reaction of $B C {l}_{3}$ with chloride ion in these terms?