Pass "object" to modular transaction methods explicitly

Summary:
Ref T13682. When editing a comment, the edit pathway may invoke file PHID extraction without first formalizing an object on the Editor.

Pass the "object" explicitly to generally improve the robustness of this pathway.

Test Plan: Edited a comment.

Maniphest Tasks: T13682

Differential Revision: https://secure.phabricator.com/D21839