When the D.C. Council debated the city’s fiscal year 2012 budget last spring, Chairman Kwame R. Brown put the kibosh on raising income taxes. He pledged before any such action a commission would be created to conduct an extensive review of the city’s tax code. The council approved legislation establishing that commission. But Mayor Vincent C. Gray hasn’t made any appointments — although he has proposed a new sales tax and the legislature eventually raised the tax rate on so-called high-income earners.