dragged

"so much time it dragged" : What does it mean? What does 'it' refer to?

A swarm of dementors was gliding amongst the trees; he could
feel their chill, and he was not sure he would be able to pass safely
through it. He had no strength left for a Patronus. He could no
longer control his own trembling. It was not, after all, so easy to
die. Every second he breathed, the smell of the grass, the cool air
on his face, was so precious: To think that people had years and
years, time to waste, so much time it dragged, and he was clinging
to each second. At the same time he thought that he would not be
able to go on, and knew that he must. The long game was ended,
the Snitch had been caught, it was time to leave the air. . .