Revitalizing Downtowns Act This bill expands the investment tax credit to add a qualified office conversion credit. The amount of such credit is 20% of the qualified conversion expenditures with respect to a qualified converted building. The bill defines qualified converted building as any building if (1) prior to conversion, the building was nonresidential real property which was leased, or available for lease, to office tenants; (2) the building has been substantially converted from an office use to a residential, retail, or other commercial use; (3) the building was initially placed in service at least 25 years prior to the beginning of the conversion, and (4) straight line depreciation is allowable with respect to the building.