Limit parent-dimensioned elements to their parent's bounds
Merge branch 'master' into background-overflow-fix
Parent-dimensioned elements should obey margins

The calculated extent we were making didn't take the final margin of the
parent into account, so we had overruns in that direction (right or
bottom).
Extract methods for retrieving extents
Merge pull request #976 from shoes/background-overflow-fix

Limit parent-dimensioned elements to their parent's bounds

* Changelog: bugfix