All glass panes (Stained and clear) and iron bars will connect to barrier blocks as they would to normal solid blocks. This does not take effect in 1.8.9, only in 1.9 snapshots (Including 1.9 Pre-Release 2 as stated)

Attachment 2016-02-20_12.10.32.png shows the panes and iron bars connected (1.9 Pre-Release 2)
Attachment 2016-02-20_12.10.15.png shows the panes and iron bars disconnected (1.8.9)