R1:6dda35897adb

Use setContentSourceFromRequest() in more places

Summary: I introduced this helper at some point, clean up all the code duplication around content sources.

Test Plan: Grepped; hit edit interfaces for most/all of these.

Reviewers: btrahan, chad, edward

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D6030