The measurement of the required depth of a front yard, or the required width of the street side yard of a corner lot, shall be horizontal and inward from the street lot line at a right angle; provided, however, that where any official right-of-way line, or any future width line pursuant to prior code Section 8-80.0, traverses the building site, the measurement here specified shall be taken from such right-of-way line, such future width line or from the street lot line, whichever produces the lesser yard. Through lots have two front lot lines, from each of which a front yard shall be measured. (Prior gen. code § 8-60.36)