I think they are the ones who are really upset because Manchester City couldn't beat Arsenal at home. For Arsenal, it was important to finish the match without losing, and I think even getting 1 point from this atmosphere made them happy. Arteta seems to have analyzed Guardiola's strategy well. He made the best defense against him.
Arteta is really good at solving Guardiola's game and collecting important points against him. He was his student at Manchester City before in the end right?
After all this effort it would be a pity if Arsenal still don't achieve the PL trophy this season. 
They really have a tough fixture waiting for them in the last weeks though.I'm okay with a champion except Manchester City. Because I want their domination to be broken. It isn't nice to see the PL turning into a farmers league you know.
If Arsenal do this job it would be a huge success after a 20-year break. If Liverpool do it Klopp would say the best kind of goodbye to this 9-year journey.