Print UI stuck when backing out of documents UI.

When user chooses to save to PDF we open the document chooser UI.
Now if the user now backs to the print UI without choosing a file,
the print UI has all options disabled and the back button does
not work - the user is stuck. This is because we were not
transitioning the print UI in the correct state.

bug:17557454

Change-Id: I385129e106ed41564b89137ca54d409127ba8ff0