KILLINGLY – In addition to adding a new line of snacks to its production line, the planned expansion of the Dayville Frito-Lay plant will also pump additional tax revenue into Killingly’s coffers. The company, already the largest employer and one of the biggest taxpayers in town, on Wednesday announced a planned $235 million expansion to its Upper Maple Street production and warehouse sites that will allow for the production of its Cheetos-brand snacks for the first time anywhere in the state. “Clearly, this will mean additional property tax revenue for Killingly,” Town Manager Mary Calorio said on Thursday. “But that revenue will be a smaller dollar amount at first.”