First step towards a Javelin behavior for Calendar day view

Summary: Ref T8300, First step towards a Javelin behavior for Calendar day view

Test Plan: No user facing changes.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8300

Differential Revision: https://secure.phabricator.com/D12978