R1:b398ae550451

Dispatch Differential edit events from Editor, not Controller

Summary:
Currently, these events don't fire for Conduit updates, which makes them sort of silly.

This will get proper treatment after T2222.

Test Plan: Installed a `throw new Exception(...)` event listener. Performed Conduit and web updates of revisions, saw event listener fire.

Reviewers: btrahan, guywarner

Reviewed By: guywarner

CC: aran

Differential Revision: https://secure.phabricator.com/D7004