Online contributions: Pay Later flag is not being passed to confirm and thank-you pages

This seems like a recent regression in online contributions. If you enable Pay Later for sample contribution page id=1 (for example), when you submit the initial form, the Confirm page is not showing the pay later info and the button title is wrong.

I've narrowed it down to the fact that $this->_params['is_pay_later'] is FALSE in Confirm::buildQuickForm() when it should be TRUE. This problem is carried through to ThankYou class as well - which 'looks like' contribution has been completed (rather than the expected Pay Later display). Note the 'green block' showing Pay Later text from my 4.5 sandbox - this doesn't appear in 4.6 now.

NOTE: The postProcess seems unaffected by this regression - the contribution is properly recorded w/ Pending Pay Later status.