When Internet gambling was launched, it was hailed by many as a potential game-changer that would help reverse years of declining revenues at what were then Atlantic City’s 12 casinos. Gov. Chris Christie’s administration expected online betting to bring in $1 billion in its first year. But only one-tenth of that — just over $111 million — has materialized. Four casinos have closed and a fifth is poised to do so next month. And one Internet gambling company, Ultimate Gaming, left the market after an unsuccessful fling with the Trump Taj Mahal.