Add inline comment support to "Pro" comment save controller

Summary: Ref T2222. Makes the "pro" controller work with inlines.

Test Plan: Added a bunch of inlines and saved them with the "pro" controller.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8306