(Portland, OR)  --  Portland police say they arrested ten people as a result of a protest at City Hall.  Demonstrators clashed with officers after the Portland City Council voted to approve a new police union contract.  The trouble began when protesters refused to leave the building after it was closed to all non-employees at 12:30 yesterday afternoon.  Authorities say one officer suffered minor injuries after being assaulted.  Protesters had cleared out by around five p.m.