patch from jst, r=danm, sr=peterv; bringing patch over from the trunk to allow "show blocked popup" to work without exposing UBW privileges to pages that did not request them git-svn-id: svn://10.0.0.236/branches/AVIARY_1_0_20040515_BRANCH@159042 18797224-902f-48f8-a5cc-f745e15eee43