Patch review request: after_save callback should not be called if a before_* callback was canceled

Hello,

I need a couple more reviews of this patch:

http://rails.lighthouseapp.com/projects/8994/tickets/1735-after_save-callback-should-not-be-called-if-a-before_-callback-was-cancelled

The patch fixes some problems related to canceling the callback chain
during the save of an ActiveRecord object. The fix and tests are
simple and straightforward, so hopefully it should be a quick review.

Thanks,

Michael