Make Differential inline events actually trigger comment preview refreshes

Summary:
Earlier, I made some changes so that when you create or edit an inline, the comment at the bottom of the page updates (even though you didn't fiddle with the stacked actions inputs).

At the last second I broke them by spelling this wrong while cleaning things up, so they didn't actually work. Spell the property correctly ("showPreview", not "shouldPreview").

Also, we have some JS which rewrites "Not Visible" into "View", but it fires in an inconvenient way now and is flickery for me. Ideally this should get cleaned up slightly better eventualy, but at least make is stop doing so much flickery layout for now.

Test Plan:

• Wrote no comment on a revision.
• Added an inline.
• Saw comment preview properly update immediately.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D17229